251999989 has 2 divisors, whose sum is σ = 251999990. Its totient is φ = 251999988.

The previous prime is 251999977. The next prime is 251999999. The reversal of 251999989 is 989999152.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 250177489 + 1822500 = 15817^2 + 1350^2 .

It is a cyclic number.

It is not a de Polignac number, because 251999989 - 2¹³ = 251991797 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251999929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125999994 + 125999995.

It is an arithmetic number, because the mean of its divisors is an integer number (125999995).

Almost surely, 2^251999989 is an apocalyptic number.

It is an amenable number.

251999989 is a deficient number, since it is larger than the sum of its proper divisors (1).

251999989 is an equidigital number, since it uses as much as digits as its factorization.

251999989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4723920, while the sum is 61.

The square root of 251999989 is about 15874.5075199201. The cubic root of 251999989 is about 631.6359505752.

The spelling of 251999989 in words is "two hundred fifty-one million, nine hundred ninety-nine thousand, nine hundred eighty-nine".