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81649664 = 2139967
BaseRepresentation
bin1001101110111…
…10000000000000
312200122020021122
410313132000000
5131400242124
612034011412
72011003445
oct467360000
9180566248
1081649664
11420a8668
1223416b68
1313bba215
14abb59cc
15727c75e
hex4dde000

81649664 has 28 divisors (see below), whose sum is σ = 163305744. Its totient is φ = 40820736.

The previous prime is 81649663. The next prime is 81649679. The reversal of 81649664 is 46694618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81649661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3209 + ... + 13175.

It is an arithmetic number, because the mean of its divisors is an integer number (5832348).

Almost surely, 281649664 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81649664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (81652872).

81649664 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

81649664 is an frugal number, since it uses more digits than its factorization.

81649664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9993 (or 9969 counting only the distinct ones).

The product of its digits is 248832, while the sum is 44.

The square root of 81649664 is about 9036.0203629695. The cubic root of 81649664 is about 433.8285546779.

The spelling of 81649664 in words is "eighty-one million, six hundred forty-nine thousand, six hundred sixty-four".

Divisors: 1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 9967 19934 39868 79736 159472 318944 637888 1275776 2551552 5103104 10206208 20412416 40824832 81649664