21493723 has 2 divisors, whose sum is σ = 21493724. Its totient is φ = 21493722.

The previous prime is 21493699. The next prime is 21493739. The reversal of 21493723 is 32739412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21493723 - 2⁵ = 21493691 is a prime.

It is not a weakly prime, because it can be changed into another prime (21494723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10746861 + 10746862.

It is an arithmetic number, because the mean of its divisors is an integer number (10746862).

Almost surely, 2^21493723 is an apocalyptic number.

21493723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21493723 is an equidigital number, since it uses as much as digits as its factorization.

21493723 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 31.

The square root of 21493723 is about 4636.1323320199. The cubic root of 21493723 is about 278.0378250208.

The spelling of 21493723 in words is "twenty-one million, four hundred ninety-three thousand, seven hundred twenty-three".