642120631 has 4 divisors (see below), whose sum is σ = 642173112. Its totient is φ = 642068152.

The previous prime is 642120623. The next prime is 642120649. The reversal of 642120631 is 136021246.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 136021246 = 2 ⋅68010623.

It is a cyclic number.

It is not a de Polignac number, because 642120631 - 2³ = 642120623 is a prime.

It is a super-2 number, since 2×642120631² = 824637809511676322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 642120596 and 642120605.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (642120691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2901 + ... + 35953.

It is an arithmetic number, because the mean of its divisors is an integer number (160543278).

Almost surely, 2^642120631 is an apocalyptic number.

642120631 is a deficient number, since it is larger than the sum of its proper divisors (52481).

642120631 is a wasteful number, since it uses less digits than its factorization.

642120631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52480.

The product of its (nonzero) digits is 1728, while the sum is 25.

The square root of 642120631 is about 25340.0992697345. The cubic root of 642120631 is about 862.7246518637.

Adding to 642120631 its reverse (136021246), we get a palindrome (778141877).

The spelling of 642120631 in words is "six hundred forty-two million, one hundred twenty thousand, six hundred thirty-one".