21469979 has 4 divisors (see below), whose sum is σ = 21521640. Its totient is φ = 21418320.

The previous prime is 21469969. The next prime is 21469999. The reversal of 21469979 is 97996412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21469979 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21469919) 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, 25202 + ... + 26039.

It is an arithmetic number, because the mean of its divisors is an integer number (5380410).

Almost surely, 2^21469979 is an apocalyptic number.

21469979 is a deficient number, since it is larger than the sum of its proper divisors (51661).

21469979 is an equidigital number, since it uses as much as digits as its factorization.

21469979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51660.

The product of its digits is 244944, while the sum is 47.

The square root of 21469979 is about 4633.5708692109. The cubic root of 21469979 is about 277.9354050014.

The spelling of 21469979 in words is "twenty-one million, four hundred sixty-nine thousand, nine hundred seventy-nine".