21479921 has 4 divisors (see below), whose sum is σ = 21556644. Its totient is φ = 21403200.

The previous prime is 21479917. The next prime is 21479957. The reversal of 21479921 is 12997412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4669921 + 16810000 = 2161^2 + 4100^2 .

It is a cyclic number.

It is not a de Polignac number, because 21479921 - 2² = 21479917 is a prime.

It is a super-2 number, since 2×21479921² = 922774012332482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21479911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 37940 + ... + 38501.

It is an arithmetic number, because the mean of its divisors is an integer number (5389161).

Almost surely, 2^21479921 is an apocalyptic number.

It is an amenable number.

21479921 is a deficient number, since it is larger than the sum of its proper divisors (76723).

21479921 is an equidigital number, since it uses as much as digits as its factorization.

21479921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76722.

The product of its digits is 9072, while the sum is 35.

The square root of 21479921 is about 4634.6435677407. The cubic root of 21479921 is about 277.9782991186.

The spelling of 21479921 in words is "twenty-one million, four hundred seventy-nine thousand, nine hundred twenty-one".