72191891 has 2 divisors, whose sum is σ = 72191892. Its totient is φ = 72191890.

The previous prime is 72191881. The next prime is 72191909. The reversal of 72191891 is 19819127.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72191891 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (72191831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36095945 + 36095946.

It is an arithmetic number, because the mean of its divisors is an integer number (36095946).

Almost surely, 2^72191891 is an apocalyptic number.

72191891 is a deficient number, since it is larger than the sum of its proper divisors (1).

72191891 is an equidigital number, since it uses as much as digits as its factorization.

72191891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 38.

The square root of 72191891 is about 8496.5811359629. The cubic root of 72191891 is about 416.3860195094.

The spelling of 72191891 in words is "seventy-two million, one hundred ninety-one thousand, eight hundred ninety-one".