72991 has 4 divisors (see below), whose sum is σ = 74592. Its totient is φ = 71392.

The previous prime is 72977. The next prime is 72997. The reversal of 72991 is 19927.

72991 = 14² + 15² + ... + 60².

72991 is nontrivially palindromic in base 15.

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 72991 - 2⁵ = 72959 is a prime.

It is a Duffinian number.

72991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72997) 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, 730 + ... + 823.

It is an arithmetic number, because the mean of its divisors is an integer number (18648).

2⁷²⁹⁹¹ is an apocalyptic number.

72991 is a deficient number, since it is larger than the sum of its proper divisors (1601).

72991 is a wasteful number, since it uses less digits than its factorization.

72991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1600.

The product of its digits is 1134, while the sum is 28.

The square root of 72991 is about 270.1684659615. The cubic root of 72991 is about 41.7916743566.

It can be divided in two parts, 729 and 91, that added together give a triangular number (820 = T₄₀).

The spelling of 72991 in words is "seventy-two thousand, nine hundred ninety-one".