81917604 has 36 divisors (see below), whose sum is σ = 207357696. Its totient is φ = 27267888.

The previous prime is 81917603. The next prime is 81917639. The reversal of 81917604 is 40671918.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81917603) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 38677 + ... + 40739.

It is an arithmetic number, because the mean of its divisors is an integer number (5759936).

Almost surely, 2^81917604 is an apocalyptic number.

It is an amenable number.

81917604 is an abundant number, since it is smaller than the sum of its proper divisors (125440092).

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

81917604 is a wasteful number, since it uses less digits than its factorization.

81917604 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3176 (or 3171 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The square root of 81917604 is about 9050.8344366694. The cubic root of 81917604 is about 434.3025844052.

The spelling of 81917604 in words is "eighty-one million, nine hundred seventeen thousand, six hundred four".