251551 has 4 divisors (see below), whose sum is σ = 262512. Its totient is φ = 240592.

The previous prime is 251543. The next prime is 251561. The reversal of 251551 is 155152.

251551 = 23² + 24² + ... + 91².

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 251551 - 2³ = 251543 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5446 + ... + 5491.

It is an arithmetic number, because the mean of its divisors is an integer number (65628).

2²⁵¹⁵⁵¹ is an apocalyptic number.

251551 is a deficient number, since it is larger than the sum of its proper divisors (10961).

251551 is a wasteful number, since it uses less digits than its factorization.

251551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10960.

The product of its digits is 250, while the sum is 19.

The square root of 251551 is about 501.5486018324. The cubic root of 251551 is about 63.1260598456.

The spelling of 251551 in words is "two hundred fifty-one thousand, five hundred fifty-one".