645877308661 has 32 divisors (see below), whose sum is σ = 724373914880. Its totient is φ = 572015001600.

The previous prime is 645877308647. The next prime is 645877308673. The reversal of 645877308661 is 166803778546.

645877308661 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 645877308661 - 2⁹ = 645877308149 is a prime.

It is a super-2 number, since 2×645877308661² (a number of 24 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (61).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645877308661.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645877308361) 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, 26209816 + ... + 26234446.

It is an arithmetic number, because the mean of its divisors is an integer number (22636684840).

Almost surely, 2^645877308661 is an apocalyptic number.

645877308661 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

645877308661 is a deficient number, since it is larger than the sum of its proper divisors (78496606219).

645877308661 is a wasteful number, since it uses less digits than its factorization.

645877308661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25517.

The product of its (nonzero) digits is 40642560, while the sum is 61.

The spelling of 645877308661 in words is "six hundred forty-five billion, eight hundred seventy-seven million, three hundred eight thousand, six hundred sixty-one".