640215253 has 4 divisors (see below), whose sum is σ = 641295468. Its totient is φ = 639135040.

The previous prime is 640215239. The next prime is 640215259. The reversal of 640215253 is 352512046.

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

It can be written as a sum of positive squares in 2 ways, for example, as 567249489 + 72965764 = 23817^2 + 8542^2 .

It is a cyclic number.

It is not a de Polignac number, because 640215253 - 2⁵ = 640215221 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640215259) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 539218 + ... + 540403.

It is an arithmetic number, because the mean of its divisors is an integer number (160323867).

Almost surely, 2^640215253 is an apocalyptic number.

It is an amenable number.

640215253 is a deficient number, since it is larger than the sum of its proper divisors (1080215).

640215253 is a wasteful number, since it uses less digits than its factorization.

640215253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1080214.

The product of its (nonzero) digits is 7200, while the sum is 28.

The square root of 640215253 is about 25302.4752346485. The cubic root of 640215253 is about 861.8704794604.

Adding to 640215253 its reverse (352512046), we get a palindrome (992727299).

The spelling of 640215253 in words is "six hundred forty million, two hundred fifteen thousand, two hundred fifty-three".