21478881 has 4 divisors (see below), whose sum is σ = 28638512. Its totient is φ = 14319252.

The previous prime is 21478867. The next prime is 21478883. The reversal of 21478881 is 18887412.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21478881 - 2⁶ = 21478817 is a prime.

It is a super-2 number, since 2×21478881² = 922684658024322, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21478883) 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, 3579811 + ... + 3579816.

It is an arithmetic number, because the mean of its divisors is an integer number (7159628).

Almost surely, 2^21478881 is an apocalyptic number.

It is an amenable number.

21478881 is a deficient number, since it is larger than the sum of its proper divisors (7159631).

21478881 is an equidigital number, since it uses as much as digits as its factorization.

21478881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7159630.

The product of its digits is 28672, while the sum is 39.

The square root of 21478881 is about 4634.5313678947. The cubic root of 21478881 is about 277.9738127257.

The spelling of 21478881 in words is "twenty-one million, four hundred seventy-eight thousand, eight hundred eighty-one".