72661981 has 8 divisors (see below), whose sum is σ = 84450240. Its totient is φ = 61225728.

The previous prime is 72661973. The next prime is 72661987. The reversal of 72661981 is 18916627.

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

It is a cyclic number.

It is not a de Polignac number, because 72661981 - 2³ = 72661973 is a prime.

It is a super-2 number, since 2×72661981² = 10559526965688722, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72661987) 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, 87556 + ... + 88381.

It is an arithmetic number, because the mean of its divisors is an integer number (10556280).

Almost surely, 2^72661981 is an apocalyptic number.

It is an amenable number.

72661981 is a deficient number, since it is larger than the sum of its proper divisors (11788259).

72661981 is a wasteful number, since it uses less digits than its factorization.

72661981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176003.

The product of its digits is 36288, while the sum is 40.

The square root of 72661981 is about 8524.1997278337. The cubic root of 72661981 is about 417.2878547385.

The spelling of 72661981 in words is "seventy-two million, six hundred sixty-one thousand, nine hundred eighty-one".