21242939 has 2 divisors, whose sum is σ = 21242940. Its totient is φ = 21242938.

The previous prime is 21242917. The next prime is 21242941. The reversal of 21242939 is 93924212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21242939 - 2¹² = 21238843 is a prime.

Together with 21242941, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21242959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10621469 + 10621470.

It is an arithmetic number, because the mean of its divisors is an integer number (10621470).

Almost surely, 2^21242939 is an apocalyptic number.

21242939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21242939 is an equidigital number, since it uses as much as digits as its factorization.

21242939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 32.

The square root of 21242939 is about 4609.0062920330. The cubic root of 21242939 is about 276.9522305944.

The spelling of 21242939 in words is "twenty-one million, two hundred forty-two thousand, nine hundred thirty-nine".