21943729 has 2 divisors, whose sum is σ = 21943730. Its totient is φ = 21943728.

The previous prime is 21943723. The next prime is 21943739. The reversal of 21943729 is 92734912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19847025 + 2096704 = 4455^2 + 1448^2 .

It is a cyclic number.

It is not a de Polignac number, because 21943729 - 2⁵ = 21943697 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21943723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10971864 + 10971865.

It is an arithmetic number, because the mean of its divisors is an integer number (10971865).

Almost surely, 2^21943729 is an apocalyptic number.

It is an amenable number.

21943729 is a deficient number, since it is larger than the sum of its proper divisors (1).

21943729 is an equidigital number, since it uses as much as digits as its factorization.

21943729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 37.

The square root of 21943729 is about 4684.4134104496. The cubic root of 21943729 is about 279.9648297662.

The spelling of 21943729 in words is "twenty-one million, nine hundred forty-three thousand, seven hundred twenty-nine".