21532721 has 8 divisors (see below), whose sum is σ = 25132800. Its totient is φ = 18063648.

The previous prime is 21532717. The next prime is 21532733. The reversal of 21532721 is 12723512.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21532721 - 2² = 21532717 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21532781) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32396 + ... + 33053.

It is an arithmetic number, because the mean of its divisors is an integer number (3141600).

Almost surely, 2^21532721 is an apocalyptic number.

It is an amenable number.

21532721 is a deficient number, since it is larger than the sum of its proper divisors (3600079).

21532721 is an equidigital number, since it uses as much as digits as its factorization.

21532721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65503.

The product of its digits is 840, while the sum is 23.

The square root of 21532721 is about 4640.3363024677. The cubic root of 21532721 is about 278.2058797894.

The spelling of 21532721 in words is "twenty-one million, five hundred thirty-two thousand, seven hundred twenty-one".