21724943 has 2 divisors, whose sum is σ = 21724944. Its totient is φ = 21724942.

The previous prime is 21724939. The next prime is 21724991. The reversal of 21724943 is 34942712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21724943 - 2² = 21724939 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21724243) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10862471 + 10862472.

It is an arithmetic number, because the mean of its divisors is an integer number (10862472).

Almost surely, 2^21724943 is an apocalyptic number.

21724943 is a deficient number, since it is larger than the sum of its proper divisors (1).

21724943 is an equidigital number, since it uses as much as digits as its factorization.

21724943 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 32.

The square root of 21724943 is about 4661.0023600080. The cubic root of 21724943 is about 279.0312739273.

The spelling of 21724943 in words is "twenty-one million, seven hundred twenty-four thousand, nine hundred forty-three".