645880646889 has 27 divisors (see below), whose sum is σ = 945176279229. Its totient is φ = 425011256280.

The previous prime is 645880646843. The next prime is 645880646899. The reversal of 645880646889 is 988646088546.

The square root of 645880646889 is 803667.

It is a perfect power (a square), and thus also a powerful number.

645880646889 is a `hidden beast` number, since 6 + 4 + 5 + 8 + 80 + 6 + 468 + 89 = 666.

645880646889 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 645880646889 - 2¹⁵ = 645880614121 is a prime.

It is not an unprimeable number, because it can be changed into a prime (645880646839) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 190467384 + ... + 190470774.

Almost surely, 2^645880646889 is an apocalyptic number.

645880646889 is the 803667-th square number.

645880646889 is the 401834-th centered octagonal number.

It is an amenable number.

645880646889 is a deficient number, since it is larger than the sum of its proper divisors (299295632340).

645880646889 is an frugal number, since it uses more digits than its factorization.

645880646889 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6946 (or 3473 counting only the distinct ones).

The product of its (nonzero) digits is 637009920, while the sum is 72.

It can be divided in two parts, 645880 and 646889, that added together give a square (1292769 = 1137²).

The spelling of 645880646889 in words is "six hundred forty-five billion, eight hundred eighty million, six hundred forty-six thousand, eight hundred eighty-nine".