81697408 has 64 divisors (see below), whose sum is σ = 181427400. Its totient is φ = 36384768.

The previous prime is 81697387. The next prime is 81697409. The reversal of 81697408 is 80479618.

It can be written as a sum of positive squares in 4 ways, for example, as 52881984 + 28815424 = 7272^2 + 5368^2 .

It is a tau number, because it is divible by the number of its divisors (64).

It is not an unprimeable number, because it can be changed into a prime (81697409) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 47410 + ... + 49102.

Almost surely, 2^81697408 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 81697408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (90713700).

81697408 is an abundant number, since it is smaller than the sum of its proper divisors (99729992).

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

81697408 is a wasteful number, since it uses less digits than its factorization.

81697408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1749 (or 1737 counting only the distinct ones).

The product of its (nonzero) digits is 96768, while the sum is 43.

The square root of 81697408 is about 9038.6618478622. The cubic root of 81697408 is about 433.9130974819.

The spelling of 81697408 in words is "eighty-one million, six hundred ninety-seven thousand, four hundred eight".