251983861 has 2 divisors, whose sum is σ = 251983862. Its totient is φ = 251983860.

The previous prime is 251983811. The next prime is 251983891. The reversal of 251983861 is 168389152.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 176624100 + 75359761 = 13290^2 + 8681^2 .

It is a cyclic number.

It is not a de Polignac number, because 251983861 - 2⁷ = 251983733 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251983811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125991930 + 125991931.

It is an arithmetic number, because the mean of its divisors is an integer number (125991931).

Almost surely, 2^251983861 is an apocalyptic number.

It is an amenable number.

251983861 is a deficient number, since it is larger than the sum of its proper divisors (1).

251983861 is an equidigital number, since it uses as much as digits as its factorization.

251983861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 103680, while the sum is 43.

The square root of 251983861 is about 15873.9995275293. Note that the first 3 decimals coincide. The cubic root of 251983861 is about 631.6224753868.

The spelling of 251983861 in words is "two hundred fifty-one million, nine hundred eighty-three thousand, eight hundred sixty-one".