72187991 has 4 divisors (see below), whose sum is σ = 72238152. Its totient is φ = 72137832.

The previous prime is 72187987. The next prime is 72188009. The reversal of 72187991 is 19978127.

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 72187991 - 2² = 72187987 is a prime.

It is a super-2 number, since 2×72187991² = 10422212089232162, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72187981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 22856 + ... + 25821.

It is an arithmetic number, because the mean of its divisors is an integer number (18059538).

Almost surely, 2^72187991 is an apocalyptic number.

72187991 is a deficient number, since it is larger than the sum of its proper divisors (50161).

72187991 is a wasteful number, since it uses less digits than its factorization.

72187991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50160.

The product of its digits is 63504, while the sum is 44.

The square root of 72187991 is about 8496.3516287875. The cubic root of 72187991 is about 416.3785212771.

The spelling of 72187991 in words is "seventy-two million, one hundred eighty-seven thousand, nine hundred ninety-one".