21381969 has 16 divisors (see below), whose sum is σ = 32696192. Its totient is φ = 12175488.

The previous prime is 21381931. The next prime is 21381977. The reversal of 21381969 is 96918312.

It is not a de Polignac number, because 21381969 - 2⁹ = 21381457 is a prime.

It is a super-2 number, since 2×21381969² = 914377196633922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21381929) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4947 + ... + 8199.

It is an arithmetic number, because the mean of its divisors is an integer number (2043512).

Almost surely, 2^21381969 is an apocalyptic number.

It is an amenable number.

21381969 is a deficient number, since it is larger than the sum of its proper divisors (11314223).

21381969 is a wasteful number, since it uses less digits than its factorization.

21381969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3576.

The product of its digits is 23328, while the sum is 39.

The square root of 21381969 is about 4624.0641215277. The cubic root of 21381969 is about 277.5551128260. Note that the first 3 decimals are identical.

The spelling of 21381969 in words is "twenty-one million, three hundred eighty-one thousand, nine hundred sixty-nine".