667979021 has 4 divisors (see below), whose sum is σ = 670640544. Its totient is φ = 665317500.

The previous prime is 667979017. The next prime is 667979027. The reversal of 667979021 is 120979766.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 667979021 - 2² = 667979017 is a prime.

It is a super-2 number, since 2×667979021² = 892391944992236882, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (667979027) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1330385 + ... + 1330886.

It is an arithmetic number, because the mean of its divisors is an integer number (167660136).

Almost surely, 2^667979021 is an apocalyptic number.

It is an amenable number.

667979021 is a deficient number, since it is larger than the sum of its proper divisors (2661523).

667979021 is a wasteful number, since it uses less digits than its factorization.

667979021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2661522.

The product of its (nonzero) digits is 285768, while the sum is 47.

The square root of 667979021 is about 25845.2901125137. The cubic root of 667979021 is about 874.1533125651.

The spelling of 667979021 in words is "six hundred sixty-seven million, nine hundred seventy-nine thousand, twenty-one".