21331969 has 4 divisors (see below), whose sum is σ = 21411540. Its totient is φ = 21252400.

The previous prime is 21331963. The next prime is 21331993. The reversal of 21331969 is 96913312.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8479744 + 12852225 = 2912^2 + 3585^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331969 - 2¹⁷ = 21200897 is a prime.

It is a super-2 number, since 2×21331969² = 910105802833922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21331963) 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, 39382 + ... + 39919.

It is an arithmetic number, because the mean of its divisors is an integer number (5352885).

It is a Proth number, since it is equal to 651 ⋅ 2¹⁵ + 1 and 651 < 2¹⁵.

Almost surely, 2^21331969 is an apocalyptic number.

It is an amenable number.

21331969 is a deficient number, since it is larger than the sum of its proper divisors (79571).

21331969 is an equidigital number, since it uses as much as digits as its factorization.

21331969 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79570.

The product of its digits is 8748, while the sum is 34.

The square root of 21331969 is about 4618.6544577398. The cubic root of 21331969 is about 277.3385972648.

The spelling of 21331969 in words is "twenty-one million, three hundred thirty-one thousand, nine hundred sixty-nine".