81655860 has 192 divisors, whose sum is σ = 278175744. Its totient is φ = 17625600.

The previous prime is 81655859. The next prime is 81655883. The reversal of 81655860 is 6855618.

It is a super-3 number, since 3×81655860³ (a number of 25 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 265827 + ... + 266133.

It is an arithmetic number, because the mean of its divisors is an integer number (1448832).

Almost surely, 2^81655860 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 81655860, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (139087872).

81655860 is an abundant number, since it is smaller than the sum of its proper divisors (196519884).

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

81655860 is a wasteful number, since it uses less digits than its factorization.

81655860 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 374 (or 372 counting only the distinct ones).

The product of its (nonzero) digits is 57600, while the sum is 39.

The square root of 81655860 is about 9036.3632065118. The cubic root of 81655860 is about 433.8395281206.

It can be divided in two parts, 816558 and 60, that added together give a palindrome (816618).

The spelling of 81655860 in words is "eighty-one million, six hundred fifty-five thousand, eight hundred sixty".