72491981 has 8 divisors (see below), whose sum is σ = 75423744. Its totient is φ = 69597360.

The previous prime is 72491971. The next prime is 72491987. The reversal of 72491981 is 18919427.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72491981 is a prime.

It is a super-2 number, since 2×72491981² = 10510174618608722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72491987) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 5270 + ... + 13143.

It is an arithmetic number, because the mean of its divisors is an integer number (9427968).

Almost surely, 2^72491981 is an apocalyptic number.

It is an amenable number.

72491981 is a deficient number, since it is larger than the sum of its proper divisors (2931763).

72491981 is a wasteful number, since it uses less digits than its factorization.

72491981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18571.

The product of its digits is 36288, while the sum is 41.

The square root of 72491981 is about 8514.2222780475. Note that the first 4 decimals coincide. The cubic root of 72491981 is about 416.9621716725.

The spelling of 72491981 in words is "seventy-two million, four hundred ninety-one thousand, nine hundred eighty-one".