642064921 has 3 divisors (see below), whose sum is σ = 642090261. Its totient is φ = 642039582.

The previous prime is 642064919. The next prime is 642064931. The reversal of 642064921 is 129460246.

The square root of 642064921 is 25339.

It is a perfect power (a square), and thus also a powerful number.

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.

It is not a de Polignac number, because 642064921 - 2¹ = 642064919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (642064931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 12670 + ... + 38008.

It is an arithmetic number, because the mean of its divisors is an integer number (214030087).

Almost surely, 2^642064921 is an apocalyptic number.

642064921 is the 25339-th square number.

642064921 is the 12670-th centered octagonal number.

It is an amenable number.

642064921 is a deficient number, since it is larger than the sum of its proper divisors (25340).

642064921 is an frugal number, since it uses more digits than its factorization.

642064921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50678 (or 25339 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 34.

The cubic root of 642064921 is about 862.6997013181.

Multiplying 642064921 by its product of nonzero digits (20736), we get a square (13313858201856 = 3648816²).

The spelling of 642064921 in words is "six hundred forty-two million, sixty-four thousand, nine hundred twenty-one".