21013979 has 8 divisors (see below), whose sum is σ = 24170208. Its totient is φ = 17896320.

The previous prime is 21013961. The next prime is 21013987. The reversal of 21013979 is 97931012.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21013979 - 2⁸ = 21013723 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21013379) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8462 + ... + 10659.

It is an arithmetic number, because the mean of its divisors is an integer number (3021276).

Almost surely, 2^21013979 is an apocalyptic number.

21013979 is a deficient number, since it is larger than the sum of its proper divisors (3156229).

21013979 is a wasteful number, since it uses less digits than its factorization.

21013979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19285.

The product of its (nonzero) digits is 3402, while the sum is 32.

The square root of 21013979 is about 4584.1006751597. The cubic root of 21013979 is about 275.9536215217.

The spelling of 21013979 in words is "twenty-one million, thirteen thousand, nine hundred seventy-nine".