640023251 has 8 divisors (see below), whose sum is σ = 746383200. Its totient is φ = 548591064.

The previous prime is 640023247. The next prime is 640023269. The reversal of 640023251 is 152320046.

It is not a de Polignac number, because 640023251 - 2² = 640023247 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640023211) 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 7 ways as a sum of consecutive naturals, for example, 932636 + ... + 933321.

It is an arithmetic number, because the mean of its divisors is an integer number (93297900).

Almost surely, 2^640023251 is an apocalyptic number.

640023251 is a deficient number, since it is larger than the sum of its proper divisors (106359949).

640023251 is an equidigital number, since it uses as much as digits as its factorization.

640023251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1865978 (or 1865964 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 640023251 is about 25298.6808154101. The cubic root of 640023251 is about 861.7843118782.

Adding to 640023251 its reverse (152320046), we get a palindrome (792343297).

The spelling of 640023251 in words is "six hundred forty million, twenty-three thousand, two hundred fifty-one".