251667561 has 8 divisors (see below), whose sum is σ = 337296160. Its totient is φ = 166908672.

The previous prime is 251667547. The next prime is 251667571. The reversal of 251667561 is 165766152.

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

It is not a de Polignac number, because 251667561 - 2⁵ = 251667529 is a prime.

It is a super-2 number, since 2×251667561² = 126673122519377442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (251667571) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 216751 + ... + 217908.

It is an arithmetic number, because the mean of its divisors is an integer number (42162020).

Almost surely, 2^251667561 is an apocalyptic number.

It is an amenable number.

251667561 is a deficient number, since it is larger than the sum of its proper divisors (85628599).

251667561 is a wasteful number, since it uses less digits than its factorization.

251667561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 434855.

The product of its digits is 75600, while the sum is 39.

The square root of 251667561 is about 15864.0335665303. The cubic root of 251667561 is about 631.3580856517.

The spelling of 251667561 in words is "two hundred fifty-one million, six hundred sixty-seven thousand, five hundred sixty-one".