21479881 has 2 divisors, whose sum is σ = 21479882. Its totient is φ = 21479880.

The previous prime is 21479873. The next prime is 21479911. The reversal of 21479881 is 18897412.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20250000 + 1229881 = 4500^2 + 1109^2 .

It is a cyclic number.

It is not a de Polignac number, because 21479881 - 2³ = 21479873 is a prime.

It is a super-2 number, since 2×21479881² = 922770575548322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21479851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10739940 + 10739941.

It is an arithmetic number, because the mean of its divisors is an integer number (10739941).

Almost surely, 2^21479881 is an apocalyptic number.

It is an amenable number.

21479881 is a deficient number, since it is larger than the sum of its proper divisors (1).

21479881 is an equidigital number, since it uses as much as digits as its factorization.

21479881 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32256, while the sum is 40.

The square root of 21479881 is about 4634.6392524122. The cubic root of 21479881 is about 277.9781265677.

The spelling of 21479881 in words is "twenty-one million, four hundred seventy-nine thousand, eight hundred eighty-one".