81599901 has 4 divisors (see below), whose sum is σ = 108799872. Its totient is φ = 54399932.

The previous prime is 81599893. The next prime is 81599951. The reversal of 81599901 is 10999518.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81599901 - 2³ = 81599893 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81599951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 13599981 + ... + 13599986.

It is an arithmetic number, because the mean of its divisors is an integer number (27199968).

Almost surely, 2^81599901 is an apocalyptic number.

It is an amenable number.

81599901 is a deficient number, since it is larger than the sum of its proper divisors (27199971).

81599901 is a wasteful number, since it uses less digits than its factorization.

81599901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27199970.

The product of its (nonzero) digits is 29160, while the sum is 42.

The square root of 81599901 is about 9033.2663527652. The cubic root of 81599901 is about 433.7404016402.

The spelling of 81599901 in words is "eighty-one million, five hundred ninety-nine thousand, nine hundred one".