21079639 has 4 divisors (see below), whose sum is σ = 24091024. Its totient is φ = 18068256.

The previous prime is 21079631. The next prime is 21079651. The reversal of 21079639 is 93697012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21079639 - 2³ = 21079631 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21079598 and 21079607.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21079631) 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, 1505682 + ... + 1505695.

It is an arithmetic number, because the mean of its divisors is an integer number (6022756).

Almost surely, 2^21079639 is an apocalyptic number.

21079639 is a deficient number, since it is larger than the sum of its proper divisors (3011385).

21079639 is an equidigital number, since it uses as much as digits as its factorization.

21079639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3011384.

The product of its (nonzero) digits is 20412, while the sum is 37.

The square root of 21079639 is about 4591.2567996138. The cubic root of 21079639 is about 276.2407363655.

The spelling of 21079639 in words is "twenty-one million, seventy-nine thousand, six hundred thirty-nine".