21387969 has 20 divisors (see below), whose sum is σ = 32408640. Its totient is φ = 14054040.

The previous prime is 21387959. The next prime is 21387973. The reversal of 21387969 is 96978312.

It is not a de Polignac number, because 21387969 - 2⁷ = 21387841 is a prime.

It is a super-2 number, since 2×21387969² = 914890435889922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21387929) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3892 + ... + 7610.

It is an arithmetic number, because the mean of its divisors is an integer number (1620432).

Almost surely, 2^21387969 is an apocalyptic number.

It is an amenable number.

21387969 is a deficient number, since it is larger than the sum of its proper divisors (11020671).

21387969 is an equidigital number, since it uses as much as digits as its factorization.

21387969 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3802 (or 3793 counting only the distinct ones).

The product of its digits is 163296, while the sum is 45.

The square root of 21387969 is about 4624.7128559512. The cubic root of 21387969 is about 277.5810720027.

The spelling of 21387969 in words is "twenty-one million, three hundred eighty-seven thousand, nine hundred sixty-nine".