21320969 has 2 divisors, whose sum is σ = 21320970. Its totient is φ = 21320968.

The previous prime is 21320947. The next prime is 21320987. The reversal of 21320969 is 96902312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 344569 = 4580^2 + 587^2 .

It is a cyclic number.

It is not a de Polignac number, because 21320969 - 2²⁴ = 4543753 is a prime.

It is a super-2 number, since 2×21320969² = 909167438197922, which contains 22 as substring.

It is a Chen prime.

It is a plaindrome in base 13.

It is not a weakly prime, because it can be changed into another prime (21328969) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660484 + 10660485.

It is an arithmetic number, because the mean of its divisors is an integer number (10660485).

Almost surely, 2^21320969 is an apocalyptic number.

It is an amenable number.

21320969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21320969 is an equidigital number, since it uses as much as digits as its factorization.

21320969 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5832, while the sum is 32.

The square root of 21320969 is about 4617.4634811767. The cubic root of 21320969 is about 277.2909184485.

The spelling of 21320969 in words is "twenty-one million, three hundred twenty thousand, nine hundred sixty-nine".