21955729 has 4 divisors (see below), whose sum is σ = 22327920. Its totient is φ = 21583540.

The previous prime is 21955711. The next prime is 21955733. The reversal of 21955729 is 92755912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21955729 - 2⁹ = 21955217 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21955691 and 21955700.

It is not an unprimeable number, because it can be changed into a prime (21955709) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 186007 + ... + 186124.

It is an arithmetic number, because the mean of its divisors is an integer number (5581980).

Almost surely, 2^21955729 is an apocalyptic number.

It is an amenable number.

21955729 is a deficient number, since it is larger than the sum of its proper divisors (372191).

21955729 is an equidigital number, since it uses as much as digits as its factorization.

21955729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 372190.

The product of its digits is 56700, while the sum is 40.

The square root of 21955729 is about 4685.6940787892. The cubic root of 21955729 is about 280.0158536942.

The spelling of 21955729 in words is "twenty-one million, nine hundred fifty-five thousand, seven hundred twenty-nine".