72166891 has 4 divisors (see below), whose sum is σ = 72352800. Its totient is φ = 71980984.

The previous prime is 72166873. The next prime is 72166901. The reversal of 72166891 is 19866127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19866127 = 349 ⋅56923.

It is a cyclic number.

It is not a de Polignac number, because 72166891 - 2⁵ = 72166859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72166841) 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, 92371 + ... + 93148.

It is an arithmetic number, because the mean of its divisors is an integer number (18088200).

Almost surely, 2^72166891 is an apocalyptic number.

72166891 is a deficient number, since it is larger than the sum of its proper divisors (185909).

72166891 is a wasteful number, since it uses less digits than its factorization.

72166891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185908.

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

The square root of 72166891 is about 8495.1098286014. The cubic root of 72166891 is about 416.3379492336.

The spelling of 72166891 in words is "seventy-two million, one hundred sixty-six thousand, eight hundred ninety-one".