251197981 has 2 divisors, whose sum is σ = 251197982. Its totient is φ = 251197980.

The previous prime is 251197957. The next prime is 251198011. The reversal of 251197981 is 189791152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 251064025 + 133956 = 15845^2 + 366^2 .

It is a cyclic number.

It is not a de Polignac number, because 251197981 - 2⁵ = 251197949 is a prime.

It is a super-2 number, since 2×251197981² = 126200851316952722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (251197901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125598990 + 125598991.

It is an arithmetic number, because the mean of its divisors is an integer number (125598991).

Almost surely, 2^251197981 is an apocalyptic number.

It is an amenable number.

251197981 is a deficient number, since it is larger than the sum of its proper divisors (1).

251197981 is an equidigital number, since it uses as much as digits as its factorization.

251197981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 43.

The square root of 251197981 is about 15849.2265110951. The cubic root of 251197981 is about 630.9651629221.

The spelling of 251197981 in words is "two hundred fifty-one million, one hundred ninety-seven thousand, nine hundred eighty-one".