251981864 has 16 divisors (see below), whose sum is σ = 476648820. Its totient is φ = 124875520.

The previous prime is 251981831. The next prime is 251981867. The reversal of 251981864 is 468189152.

It can be written as a sum of positive squares in 2 ways, for example, as 238949764 + 13032100 = 15458^2 + 3610^2 .

It is not an unprimeable number, because it can be changed into a prime (251981867) 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, 138467 + ... + 140274.

Almost surely, 2^251981864 is an apocalyptic number.

It is an amenable number.

251981864 is a deficient number, since it is larger than the sum of its proper divisors (224666956).

251981864 is a wasteful number, since it uses less digits than its factorization.

251981864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 278860 (or 278856 counting only the distinct ones).

The product of its digits is 138240, while the sum is 44.

The square root of 251981864 is about 15873.9366258027. The cubic root of 251981864 is about 631.6208068231.

The spelling of 251981864 in words is "two hundred fifty-one million, nine hundred eighty-one thousand, eight hundred sixty-four".