642115021 has 2 divisors, whose sum is σ = 642115022. Its totient is φ = 642115020.

The previous prime is 642114947. The next prime is 642115031. The reversal of 642115021 is 120511246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 625550121 + 16564900 = 25011^2 + 4070^2 .

It is a cyclic number.

It is not a de Polignac number, because 642115021 - 2²³ = 633726413 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 642114983 and 642115001.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642115031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321057510 + 321057511.

It is an arithmetic number, because the mean of its divisors is an integer number (321057511).

Almost surely, 2^642115021 is an apocalyptic number.

It is an amenable number.

642115021 is a deficient number, since it is larger than the sum of its proper divisors (1).

642115021 is an equidigital number, since it uses as much as digits as its factorization.

642115021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 642115021 is about 25339.9885753723. The cubic root of 642115021 is about 862.7221394078.

Adding to 642115021 its reverse (120511246), we get a palindrome (762626267).

The spelling of 642115021 in words is "six hundred forty-two million, one hundred fifteen thousand, twenty-one".