21477881 has 4 divisors (see below), whose sum is σ = 21523200. Its totient is φ = 21432564.

The previous prime is 21477877. The next prime is 21477889. The reversal of 21477881 is 18877412.

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 a cyclic number.

It is not a de Polignac number, because 21477881 - 2² = 21477877 is a prime.

It is a super-2 number, since 2×21477881² = 922598744500322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21477889) 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, 21941 + ... + 22898.

It is an arithmetic number, because the mean of its divisors is an integer number (5380800).

Almost surely, 2^21477881 is an apocalyptic number.

It is an amenable number.

21477881 is a deficient number, since it is larger than the sum of its proper divisors (45319).

21477881 is an equidigital number, since it uses as much as digits as its factorization.

21477881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 45318.

The product of its digits is 25088, while the sum is 38.

The square root of 21477881 is about 4634.4234808658. The cubic root of 21477881 is about 277.9694987498.

The spelling of 21477881 in words is "twenty-one million, four hundred seventy-seven thousand, eight hundred eighty-one".