21931243 has 2 divisors, whose sum is σ = 21931244. Its totient is φ = 21931242.

The previous prime is 21931237. The next prime is 21931253. The reversal of 21931243 is 34213912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21931243 - 2⁵ = 21931211 is a prime.

It is not a weakly prime, because it can be changed into another prime (21931223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10965621 + 10965622.

It is an arithmetic number, because the mean of its divisors is an integer number (10965622).

Almost surely, 2^21931243 is an apocalyptic number.

21931243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21931243 is an equidigital number, since it uses as much as digits as its factorization.

21931243 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 25.

The square root of 21931243 is about 4683.0805032585. The cubic root of 21931243 is about 279.9117196182.

The spelling of 21931243 in words is "twenty-one million, nine hundred thirty-one thousand, two hundred forty-three".