645640590 has 64 divisors (see below), whose sum is σ = 1847909376. Its totient is φ = 141157632.

The previous prime is 645640553. The next prime is 645640591. The reversal of 645640590 is 95046546.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645640591) 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 31 ways as a sum of consecutive naturals, for example, 62007 + ... + 71666.

It is an arithmetic number, because the mean of its divisors is an integer number (28873584).

Almost surely, 2^645640590 is an apocalyptic number.

645640590 is an abundant number, since it is smaller than the sum of its proper divisors (1202268786).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645640590 is a wasteful number, since it uses less digits than its factorization.

645640590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133713.

The product of its (nonzero) digits is 129600, while the sum is 39.

The square root of 645640590 is about 25409.4586719198. The cubic root of 645640590 is about 864.2982000727.

The spelling of 645640590 in words is "six hundred forty-five million, six hundred forty thousand, five hundred ninety".