642118921 has 2 divisors, whose sum is σ = 642118922. Its totient is φ = 642118920.

The previous prime is 642118907. The next prime is 642118931. The reversal of 642118921 is 129811246.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 532686400 + 109432521 = 23080^2 + 10461^2 .

It is a cyclic number.

It is not a de Polignac number, because 642118921 - 2¹⁵ = 642086153 is a prime.

It is not a weakly prime, because it can be changed into another prime (642118931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321059460 + 321059461.

It is an arithmetic number, because the mean of its divisors is an integer number (321059461).

Almost surely, 2^642118921 is an apocalyptic number.

It is an amenable number.

642118921 is a deficient number, since it is larger than the sum of its proper divisors (1).

642118921 is an equidigital number, since it uses as much as digits as its factorization.

642118921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6912, while the sum is 34.

The square root of 642118921 is about 25340.0655287235. The cubic root of 642118921 is about 862.7238860365.

The spelling of 642118921 in words is "six hundred forty-two million, one hundred eighteen thousand, nine hundred twenty-one".