645616811989 has 2 divisors, whose sum is σ = 645616811990. Its totient is φ = 645616811988.

The previous prime is 645616811921. The next prime is 645616812013. The reversal of 645616811989 is 989118616546.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 487385496900 + 158231315089 = 698130^2 + 397783^2 .

It is a cyclic number.

It is not a de Polignac number, because 645616811989 - 2²¹ = 645614714837 is a prime.

It is a super-2 number, since 2×645616811989² (a number of 24 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 645616811989.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645616511989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322808405994 + 322808405995.

It is an arithmetic number, because the mean of its divisors is an integer number (322808405995).

Almost surely, 2^645616811989 is an apocalyptic number.

It is an amenable number.

645616811989 is a deficient number, since it is larger than the sum of its proper divisors (1).

645616811989 is an equidigital number, since it uses as much as digits as its factorization.

645616811989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22394880, while the sum is 64.

The spelling of 645616811989 in words is "six hundred forty-five billion, six hundred sixteen million, eight hundred eleven thousand, nine hundred eighty-nine".