251920409 has 8 divisors (see below), whose sum is σ = 273121800. Its totient is φ = 230979456.

The previous prime is 251920393. The next prime is 251920429. The reversal of 251920409 is 904029152.

It can be written as a sum of positive squares in 4 ways, for example, as 25 + 251920384 = 5^2 + 15872^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 251920409 - 2⁴ = 251920393 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (251920429) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 63092 + ... + 66965.

It is an arithmetic number, because the mean of its divisors is an integer number (34140225).

Almost surely, 2^251920409 is an apocalyptic number.

It is an amenable number.

251920409 is a deficient number, since it is larger than the sum of its proper divisors (21201391).

251920409 is a wasteful number, since it uses less digits than its factorization.

251920409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130219.

The product of its (nonzero) digits is 6480, while the sum is 32.

The square root of 251920409 is about 15872.0007875504. Note that the first 3 decimals coincide. The cubic root of 251920409 is about 631.5694546978.

The spelling of 251920409 in words is "two hundred fifty-one million, nine hundred twenty thousand, four hundred nine".