21702561 has 8 divisors (see below), whose sum is σ = 29262240. Its totient is φ = 14305632.

The previous prime is 21702539. The next prime is 21702563. The reversal of 21702561 is 16520712.

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

It is not a de Polignac number, because 21702561 - 2⁵ = 21702529 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21702563) 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, 40375 + ... + 40908.

It is an arithmetic number, because the mean of its divisors is an integer number (3657780).

Almost surely, 2^21702561 is an apocalyptic number.

It is an amenable number.

21702561 is a deficient number, since it is larger than the sum of its proper divisors (7559679).

21702561 is an equidigital number, since it uses as much as digits as its factorization.

21702561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81375.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21702561 is about 4658.6007555917. The cubic root of 21702561 is about 278.9354175359.

The spelling of 21702561 in words is "twenty-one million, seven hundred two thousand, five hundred sixty-one".