251550661 has 4 divisors (see below), whose sum is σ = 251715232. Its totient is φ = 251386092.

The previous prime is 251550659. The next prime is 251550697. The reversal of 251550661 is 166055152.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 251550661 - 2¹ = 251550659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251850661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 79971 + ... + 83056.

It is an arithmetic number, because the mean of its divisors is an integer number (62928808).

Almost surely, 2^251550661 is an apocalyptic number.

It is an amenable number.

251550661 is a deficient number, since it is larger than the sum of its proper divisors (164571).

251550661 is a wasteful number, since it uses less digits than its factorization.

251550661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 164570.

The product of its (nonzero) digits is 9000, while the sum is 31.

The square root of 251550661 is about 15860.3487036067. The cubic root of 251550661 is about 631.2603148855.

The spelling of 251550661 in words is "two hundred fifty-one million, five hundred fifty thousand, six hundred sixty-one".