81608640 has 56 divisors (see below), whose sum is σ = 259110480. Its totient is φ = 21762048.

The previous prime is 81608633. The next prime is 81608729. The reversal of 81608640 is 4680618.

It is a super-3 number, since 3×81608640³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41545 + ... + 43464.

Almost surely, 2^81608640 is an apocalyptic number.

81608640 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

81608640 is an abundant number, since it is smaller than the sum of its proper divisors (177501840).

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

81608640 is a wasteful number, since it uses less digits than its factorization.

81608640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85029 (or 85019 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 33.

The square root of 81608640 is about 9033.7500518888. The cubic root of 81608640 is about 433.7558850007.

The spelling of 81608640 in words is "eighty-one million, six hundred eight thousand, six hundred forty".