21431939 has 2 divisors, whose sum is σ = 21431940. Its totient is φ = 21431938.

The previous prime is 21431933. The next prime is 21431959. The reversal of 21431939 is 93913412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21431939 - 2¹² = 21427843 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21431933) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10715969 + 10715970.

It is an arithmetic number, because the mean of its divisors is an integer number (10715970).

Almost surely, 2^21431939 is an apocalyptic number.

21431939 is a deficient number, since it is larger than the sum of its proper divisors (1).

21431939 is an equidigital number, since it uses as much as digits as its factorization.

21431939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5832, while the sum is 32.

The square root of 21431939 is about 4629.4642238600. The cubic root of 21431939 is about 277.7711615076.

The spelling of 21431939 in words is "twenty-one million, four hundred thirty-one thousand, nine hundred thirty-nine".