81615680 has 28 divisors (see below), whose sum is σ = 194348100. Its totient is φ = 32646144.

The previous prime is 81615631. The next prime is 81615713. The reversal of 81615680 is 8651618.

It can be written as a sum of positive squares in 2 ways, for example, as 41267776 + 40347904 = 6424^2 + 6352^2 .

It is a super-2 number, since 2×81615680² = 13322238443724800, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81615680.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 127205 + ... + 127844.

Almost surely, 2^81615680 is an apocalyptic number.

81615680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81615680 is an abundant number, since it is smaller than the sum of its proper divisors (112732420).

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

81615680 is a wasteful number, since it uses less digits than its factorization.

81615680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 255066 (or 255056 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 35.

The square root of 81615680 is about 9034.1396934074. The cubic root of 81615680 is about 433.7683573469.

The spelling of 81615680 in words is "eighty-one million, six hundred fifteen thousand, six hundred eighty".