640156251 has 16 divisors (see below), whose sum is σ = 976405248. Its totient is φ = 365455200.

The previous prime is 640156243. The next prime is 640156273. The reversal of 640156251 is 152651046.

640156251 = T₄₉₁ + T₄₉₂ + ... + T₁₅₈₁.

It is not a de Polignac number, because 640156251 - 2³ = 640156243 is a prime.

It is not an unprimeable number, because it can be changed into a prime (640156241) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8941 + ... + 36881.

It is an arithmetic number, because the mean of its divisors is an integer number (61025328).

Almost surely, 2^640156251 is an apocalyptic number.

640156251 is a deficient number, since it is larger than the sum of its proper divisors (336248997).

640156251 is a wasteful number, since it uses less digits than its factorization.

640156251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29042.

The product of its (nonzero) digits is 7200, while the sum is 30.

The square root of 640156251 is about 25301.3092744229. The cubic root of 640156251 is about 861.8440020926.

The spelling of 640156251 in words is "six hundred forty million, one hundred fifty-six thousand, two hundred fifty-one".