251878781 has 32 divisors (see below), whose sum is σ = 325140480. Its totient is φ = 189446400.

The previous prime is 251878769. The next prime is 251878787. The reversal of 251878781 is 187878152.

It is not a de Polignac number, because 251878781 - 2¹⁰ = 251877757 is a prime.

It is a super-2 number, since 2×251878781² = 126885840636091922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (47).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (251878787) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 285461 + ... + 286341.

It is an arithmetic number, because the mean of its divisors is an integer number (10160640).

Almost surely, 2^251878781 is an apocalyptic number.

It is an amenable number.

251878781 is a deficient number, since it is larger than the sum of its proper divisors (73261699).

251878781 is a wasteful number, since it uses less digits than its factorization.

251878781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1025.

The product of its digits is 250880, while the sum is 47.

The square root of 251878781 is about 15870.6893675102. The cubic root of 251878781 is about 631.5346653747.

The spelling of 251878781 in words is "two hundred fifty-one million, eight hundred seventy-eight thousand, seven hundred eighty-one".