645606556020 has 36 divisors (see below), whose sum is σ = 1958339887140. Its totient is φ = 172161748224.

The previous prime is 645606555929. The next prime is 645606556079. The reversal of 645606556020 is 20655606546.

It is a happy number.

645606556020 is a `hidden beast` number, since 6 + 4 + 5 + 6 + 0 + 65 + 560 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 212995172196 + 432611383824 = 461514^2 + 657732^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1793351365 + ... + 1793351724.

Almost surely, 2^645606556020 is an apocalyptic number.

645606556020 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

645606556020 is an abundant number, since it is smaller than the sum of its proper divisors (1312733331120).

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

645606556020 is a wasteful number, since it uses less digits than its factorization.

645606556020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3586703104 (or 3586703099 counting only the distinct ones).

The product of its (nonzero) digits is 1296000, while the sum is 45.

The spelling of 645606556020 in words is "six hundred forty-five billion, six hundred six million, five hundred fifty-six thousand, twenty".