81604917 has 6 divisors (see below), whose sum is σ = 117873782. Its totient is φ = 54403272.

The previous prime is 81604909. The next prime is 81604931. The reversal of 81604917 is 71940618.

81604917 is a `hidden beast` number, since 8 + 160 + 491 + 7 = 666.

It can be written as a sum of positive squares in only one way, i.e., 79548561 + 2056356 = 8919^2 + 1434^2 .

It is not a de Polignac number, because 81604917 - 2³ = 81604909 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81604967) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4533598 + ... + 4533615.

Almost surely, 2^81604917 is an apocalyptic number.

It is an amenable number.

81604917 is a deficient number, since it is larger than the sum of its proper divisors (36268865).

81604917 is a wasteful number, since it uses less digits than its factorization.

81604917 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9067219 (or 9067216 counting only the distinct ones).

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

The square root of 81604917 is about 9033.5439889337. The cubic root of 81604917 is about 433.7492888947.

The spelling of 81604917 in words is "eighty-one million, six hundred four thousand, nine hundred seventeen".