645880646890 has 64 divisors (see below), whose sum is σ = 1187881057440. Its totient is φ = 252798566400.

The previous prime is 645880646843. The next prime is 645880646899. The reversal of 645880646890 is 98646088546.

645880646890 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Cunningham number, because it is equal to 803667²+1.

It can be written as a sum of positive squares in 16 ways, for example, as 119259024921 + 526621621969 = 345339^2 + 725687^2 .

It is not an unprimeable number, because it can be changed into a prime (645880646899) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 75334644 + ... + 75343216.

Almost surely, 2^645880646890 is an apocalyptic number.

645880646890 is a deficient number, since it is larger than the sum of its proper divisors (542000410550).

645880646890 is a wasteful number, since it uses less digits than its factorization.

645880646890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9547.

The product of its (nonzero) digits is 79626240, while the sum is 64.

The spelling of 645880646890 in words is "six hundred forty-five billion, eight hundred eighty million, six hundred forty-six thousand, eight hundred ninety".