645691020 has 48 divisors (see below), whose sum is σ = 1947009120. Its totient is φ = 158939136.

The previous prime is 645691019. The next prime is 645691021. The reversal of 645691020 is 20196546.

It is an interprime number because it is at equal distance from previous prime (645691019) and next prime (645691021).

It is not an unprimeable number, because it can be changed into a prime (645691021) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 413125 + ... + 414684.

It is an arithmetic number, because the mean of its divisors is an integer number (40562690).

Almost surely, 2^645691020 is an apocalyptic number.

645691020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645691020 is an abundant number, since it is smaller than the sum of its proper divisors (1301318100).

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

645691020 is a wasteful number, since it uses less digits than its factorization.

645691020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 827834 (or 827832 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 33.

The square root of 645691020 is about 25410.4509995395. The cubic root of 645691020 is about 864.3207024907.

The spelling of 645691020 in words is "six hundred forty-five million, six hundred ninety-one thousand, twenty".