21872369 has 2 divisors, whose sum is σ = 21872370. Its totient is φ = 21872368.

The previous prime is 21872341. The next prime is 21872371. The reversal of 21872369 is 96327812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17305600 + 4566769 = 4160^2 + 2137^2 .

It is a cyclic number.

It is not a de Polignac number, because 21872369 - 2⁸ = 21872113 is a prime.

It is a super-2 number, since 2×21872369² = 956801051344322, which contains 22 as substring.

Together with 21872371, it forms a pair of twin primes.

It is a Chen prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21872309) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936184 + 10936185.

It is an arithmetic number, because the mean of its divisors is an integer number (10936185).

Almost surely, 2^21872369 is an apocalyptic number.

It is an amenable number.

21872369 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872369 is an equidigital number, since it uses as much as digits as its factorization.

21872369 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 38.

The square root of 21872369 is about 4676.7904592787. The cubic root of 21872369 is about 279.6610226113.

The spelling of 21872369 in words is "twenty-one million, eight hundred seventy-two thousand, three hundred sixty-nine".