21872231 has 2 divisors, whose sum is σ = 21872232. Its totient is φ = 21872230.

The previous prime is 21872209. The next prime is 21872237. The reversal of 21872231 is 13227812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21872231 - 2¹⁰ = 21871207 is a prime.

It is a super-2 number, since 2×21872231² = 956788977834722, which contains 22 as substring.

It is a Chen prime.

It is equal to p_1381652 and since 21872231 and 1381652 have the same sum of digits, it is a Honaker prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21872231.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21872237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936115 + 10936116.

It is an arithmetic number, because the mean of its divisors is an integer number (10936116).

Almost surely, 2^21872231 is an apocalyptic number.

21872231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21872231 is an equidigital number, since it uses as much as digits as its factorization.

21872231 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1344, while the sum is 26.

The square root of 21872231 is about 4676.7757055476. The cubic root of 21872231 is about 279.6604344522.

The spelling of 21872231 in words is "twenty-one million, eight hundred seventy-two thousand, two hundred thirty-one".