2172985891 has 2 divisors, whose sum is σ = 2172985892. Its totient is φ = 2172985890.

The previous prime is 2172985879. The next prime is 2172985897. The reversal of 2172985891 is 1985892712.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2172985891 is a prime.

It is not a weakly prime, because it can be changed into another prime (2172985897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1086492945 + 1086492946.

It is an arithmetic number, because the mean of its divisors is an integer number (1086492946).

Almost surely, 2^2172985891 is an apocalyptic number.

2172985891 is a deficient number, since it is larger than the sum of its proper divisors (1).

2172985891 is an equidigital number, since it uses as much as digits as its factorization.

2172985891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 725760, while the sum is 52.

The square root of 2172985891 is about 46615.2967490286. The cubic root of 2172985891 is about 1295.2461264518.

The spelling of 2172985891 in words is "two billion, one hundred seventy-two million, nine hundred eighty-five thousand, eight hundred ninety-one".