81765560 has 64 divisors (see below), whose sum is σ = 191164320. Its totient is φ = 31449600.

The previous prime is 81765539. The next prime is 81765577. The reversal of 81765560 is 6556718.

It is a happy number.

It is a super-2 number, since 2×81765560² = 13371213604227200, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 149207 + ... + 149753.

Almost surely, 2^81765560 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 81765560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (95582160).

81765560 is an abundant number, since it is smaller than the sum of its proper divisors (109398760).

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

81765560 is a wasteful number, since it uses less digits than its factorization.

81765560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 696 (or 692 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 38.

The square root of 81765560 is about 9042.4310890379. The cubic root of 81765560 is about 434.0337207548.

The spelling of 81765560 in words is "eighty-one million, seven hundred sixty-five thousand, five hundred sixty".