645606556021 has 8 divisors (see below), whose sum is σ = 741332919104. Its totient is φ = 550754406720.

The previous prime is 645606555929. The next prime is 645606556079. The reversal of 645606556021 is 120655606546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-645606556021 is a prime.

It is a super-2 number, since 2×645606556021² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645606556921) 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 7 ways as a sum of consecutive naturals, for example, 218551860 + ... + 218554813.

It is an arithmetic number, because the mean of its divisors is an integer number (92666614888).

Almost surely, 2^645606556021 is an apocalyptic number.

It is an amenable number.

645606556021 is a deficient number, since it is larger than the sum of its proper divisors (95726363083).

645606556021 is a wasteful number, since it uses less digits than its factorization.

645606556021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 437106891.

The product of its (nonzero) digits is 1296000, while the sum is 46.

The spelling of 645606556021 in words is "six hundred forty-five billion, six hundred six million, five hundred fifty-six thousand, twenty-one".