251666 has 8 divisors (see below), whose sum is σ = 393984. Its totient is φ = 120340.

The previous prime is 251663. The next prime is 251677. The reversal of 251666 is 666152.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 251666.

It is not an unprimeable number, because it can be changed into a prime (251663) 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, 2690 + ... + 2781.

It is an arithmetic number, because the mean of its divisors is an integer number (49248).

2²⁵¹⁶⁶⁶ is an apocalyptic number.

251666 is a deficient number, since it is larger than the sum of its proper divisors (142318).

251666 is a wasteful number, since it uses less digits than its factorization.

251666 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5496.

The product of its digits is 2160, while the sum is 26.

The square root of 251666 is about 501.6632336538. The cubic root of 251666 is about 63.1356780289.

The spelling of 251666 in words is "two hundred fifty-one thousand, six hundred sixty-six".