642977989 has 2 divisors, whose sum is σ = 642977990. Its totient is φ = 642977988.

The previous prime is 642977969. The next prime is 642978043. The reversal of 642977989 is 989779246.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 398681089 + 244296900 = 19967^2 + 15630^2 .

It is a cyclic number.

It is not a de Polignac number, because 642977989 - 2¹⁵ = 642945221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642977939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321488994 + 321488995.

It is an arithmetic number, because the mean of its divisors is an integer number (321488995).

Almost surely, 2^642977989 is an apocalyptic number.

It is an amenable number.

642977989 is a deficient number, since it is larger than the sum of its proper divisors (1).

642977989 is an equidigital number, since it uses as much as digits as its factorization.

642977989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13716864, while the sum is 61.

The square root of 642977989 is about 25357.0106479451. The cubic root of 642977989 is about 863.1084504270.

The spelling of 642977989 in words is "six hundred forty-two million, nine hundred seventy-seven thousand, nine hundred eighty-nine".