21865331 has 2 divisors, whose sum is σ = 21865332. Its totient is φ = 21865330.

The previous prime is 21865289. The next prime is 21865339. The reversal of 21865331 is 13356812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21865331 - 2¹⁴ = 21848947 is a prime.

It is a super-2 number, since 2×21865331² = 956185399479122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a junction number, because it is equal to n+sod(n) for n = 21865294 and 21865303.

It is not a weakly prime, because it can be changed into another prime (21865339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932665 + 10932666.

It is an arithmetic number, because the mean of its divisors is an integer number (10932666).

Almost surely, 2^21865331 is an apocalyptic number.

21865331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865331 is an equidigital number, since it uses as much as digits as its factorization.

21865331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 29.

The square root of 21865331 is about 4676.0379596406. The cubic root of 21865331 is about 279.6310233395.

The spelling of 21865331 in words is "twenty-one million, eight hundred sixty-five thousand, three hundred thirty-one".