21381885 has 36 divisors (see below), whose sum is σ = 43117308. Its totient is φ = 9773568.

The previous prime is 21381853. The next prime is 21381887. The reversal of 21381885 is 58818312.

It can be written as a sum of positive squares in 2 ways, for example, as 4955076 + 16426809 = 2226^2 + 4053^2 .

It is not a de Polignac number, because 21381885 - 2⁵ = 21381853 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21381887) 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 35 ways as a sum of consecutive naturals, for example, 2644 + ... + 7053.

It is an arithmetic number, because the mean of its divisors is an integer number (1197703).

Almost surely, 2^21381885 is an apocalyptic number.

It is an amenable number.

21381885 is an abundant number, since it is smaller than the sum of its proper divisors (21735423).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21381885 is a wasteful number, since it uses less digits than its factorization.

21381885 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9722 (or 9712 counting only the distinct ones).

The product of its digits is 15360, while the sum is 36.

The square root of 21381885 is about 4624.0550385998. The cubic root of 21381885 is about 277.5547493631.

The spelling of 21381885 in words is "twenty-one million, three hundred eighty-one thousand, eight hundred eighty-five".