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81911808 = 2133211101
BaseRepresentation
bin1001110000111…
…10000000000000
312201010112212200
410320132000000
5131432134213
612043353200
72013144636
oct470360000
9181115780
1081911808
1142267610
1223522800
1313c7c634
14ac43356
1572d0273
hex4e1e000

81911808 has 168 divisors, whose sum is σ = 260686296. Its totient is φ = 24576000.

The previous prime is 81911771. The next prime is 81911813. The reversal of 81911808 is 80811918.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 810958 + ... + 811058.

Almost surely, 281911808 is an apocalyptic number.

81911808 is a gapful number since it is divisible by the number (88) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81911808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130343148).

81911808 is an abundant number, since it is smaller than the sum of its proper divisors (178774488).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81911808 is a wasteful number, since it uses less digits than its factorization.

81911808 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144 (or 117 counting only the distinct ones).

The product of its (nonzero) digits is 4608, while the sum is 36.

The square root of 81911808 is about 9050.5142395336. The cubic root of 81911808 is about 434.2923412786.

It can be divided in two parts, 8191 and 1808, that added together give a palindrome (9999).

The spelling of 81911808 in words is "eighty-one million, nine hundred eleven thousand, eight hundred eight".