640232521 has 2 divisors, whose sum is σ = 640232522. Its totient is φ = 640232520.

The previous prime is 640232519. The next prime is 640232533. The reversal of 640232521 is 125232046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 337089600 + 303142921 = 18360^2 + 17411^2 .

It is a cyclic number.

It is not a de Polignac number, because 640232521 - 2¹ = 640232519 is a prime.

Together with 640232519, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (640232591) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320116260 + 320116261.

It is an arithmetic number, because the mean of its divisors is an integer number (320116261).

Almost surely, 2^640232521 is an apocalyptic number.

It is an amenable number.

640232521 is a deficient number, since it is larger than the sum of its proper divisors (1).

640232521 is an equidigital number, since it uses as much as digits as its factorization.

640232521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 640232521 is about 25302.8164637852. The cubic root of 640232521 is about 861.8782282322.

Adding to 640232521 its reverse (125232046), we get a palindrome (765464567).

The spelling of 640232521 in words is "six hundred forty million, two hundred thirty-two thousand, five hundred twenty-one".