251668840 has 16 divisors (see below), whose sum is σ = 566254980. Its totient is φ = 100667520.

The previous prime is 251668811. The next prime is 251668841. The reversal of 251668840 is 48866152.

It can be written as a sum of positive squares in 2 ways, for example, as 238578916 + 13089924 = 15446^2 + 3618^2 .

It is a Harshad number since it is a multiple of its sum of digits (40), and also a Moran number because the ratio is a prime number: 6291721 = 251668840 / (2 + 5 + 1 + 6 + 6 + 8 + 8 + 4 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 251668793 and 251668802.

It is not an unprimeable number, because it can be changed into a prime (251668841) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3145821 + ... + 3145900.

Almost surely, 2^251668840 is an apocalyptic number.

251668840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

251668840 is an abundant number, since it is smaller than the sum of its proper divisors (314586140).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

251668840 is a wasteful number, since it uses less digits than its factorization.

251668840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6291732 (or 6291728 counting only the distinct ones).

The product of its (nonzero) digits is 92160, while the sum is 40.

The square root of 251668840 is about 15864.0738777907. The cubic root of 251668840 is about 631.3591551918.

The spelling of 251668840 in words is "two hundred fifty-one million, six hundred sixty-eight thousand, eight hundred forty".