21493739 has 2 divisors, whose sum is σ = 21493740. Its totient is φ = 21493738.

The previous prime is 21493723. The next prime is 21493751. The reversal of 21493739 is 93739412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21493739 - 2⁴ = 21493723 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21493789) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746869 + 10746870.

It is an arithmetic number, because the mean of its divisors is an integer number (10746870).

Almost surely, 2^21493739 is an apocalyptic number.

21493739 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493739 is an equidigital number, since it uses as much as digits as its factorization.

21493739 is an evil number, because the sum of its binary digits is even.

The product of its digits is 40824, while the sum is 38.

The square root of 21493739 is about 4636.1340575958. The cubic root of 21493739 is about 278.0378940115.

The spelling of 21493739 in words is "twenty-one million, four hundred ninety-three thousand, seven hundred thirty-nine".