640624251 has 4 divisors (see below), whose sum is σ = 854165672. Its totient is φ = 427082832.

The previous prime is 640624249. The next prime is 640624289. The reversal of 640624251 is 152426046.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 640624251 - 2¹ = 640624249 is a prime.

It is a super-2 number, since 2×640624251² = 820798861938622002, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640624291) 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 3 ways as a sum of consecutive naturals, for example, 106770706 + ... + 106770711.

It is an arithmetic number, because the mean of its divisors is an integer number (213541418).

Almost surely, 2^640624251 is an apocalyptic number.

640624251 is a deficient number, since it is larger than the sum of its proper divisors (213541421).

640624251 is a wasteful number, since it uses less digits than its factorization.

640624251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213541420.

The product of its (nonzero) digits is 11520, while the sum is 30.

The square root of 640624251 is about 25310.5561179521. The cubic root of 640624251 is about 862.0539741327.

The spelling of 640624251 in words is "six hundred forty million, six hundred twenty-four thousand, two hundred fifty-one".