251906491 has 2 divisors, whose sum is σ = 251906492. Its totient is φ = 251906490.

The previous prime is 251906477. The next prime is 251906497. The reversal of 251906491 is 194609152.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 251906491 - 2⁷ = 251906363 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 251906491.

It is not a weakly prime, because it can be changed into another prime (251906497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125953245 + 125953246.

It is an arithmetic number, because the mean of its divisors is an integer number (125953246).

Almost surely, 2^251906491 is an apocalyptic number.

251906491 is a deficient number, since it is larger than the sum of its proper divisors (1).

251906491 is an equidigital number, since it uses as much as digits as its factorization.

251906491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 19440, while the sum is 37.

The square root of 251906491 is about 15871.5623364557. The cubic root of 251906491 is about 631.5578235831.

The spelling of 251906491 in words is "two hundred fifty-one million, nine hundred six thousand, four hundred ninety-one".