251121133561 has 2 divisors, whose sum is σ = 251121133562. Its totient is φ = 251121133560.

The previous prime is 251121133559. The next prime is 251121133639. The reversal of 251121133561 is 165331121152.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 249300490000 + 1820643561 = 499300^2 + 42669^2 .

It is a cyclic number.

It is not a de Polignac number, because 251121133561 - 2¹ = 251121133559 is a prime.

It is a super-4 number, since 4×251121133561⁴ (a number of 47 digits) contains 4444 as substring.

Together with 251121133559, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (251121131561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 125560566780 + 125560566781.

It is an arithmetic number, because the mean of its divisors is an integer number (125560566781).

Almost surely, 2^251121133561 is an apocalyptic number.

It is an amenable number.

251121133561 is a deficient number, since it is larger than the sum of its proper divisors (1).

251121133561 is an equidigital number, since it uses as much as digits as its factorization.

251121133561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5400, while the sum is 31.

The spelling of 251121133561 in words is "two hundred fifty-one billion, one hundred twenty-one million, one hundred thirty-three thousand, five hundred sixty-one".