81072591 has 4 divisors (see below), whose sum is σ = 108096792. Its totient is φ = 54048392.

The previous prime is 81072581. The next prime is 81072617. The reversal of 81072591 is 19527018.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 81072591 - 2¹⁵ = 81039823 is a prime.

It is a super-2 number, since 2×81072591² = 13145530022906562, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81072521) 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, 13512096 + ... + 13512101.

It is an arithmetic number, because the mean of its divisors is an integer number (27024198).

Almost surely, 2^81072591 is an apocalyptic number.

81072591 is a deficient number, since it is larger than the sum of its proper divisors (27024201).

81072591 is a wasteful number, since it uses less digits than its factorization.

81072591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27024200.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 81072591 is about 9004.0319301966. The cubic root of 81072591 is about 432.8040847699.

The spelling of 81072591 in words is "eighty-one million, seventy-two thousand, five hundred ninety-one".