21410721 has 12 divisors (see below), whose sum is σ = 31389072. Its totient is φ = 14060376.

The previous prime is 21410699. The next prime is 21410731. The reversal of 21410721 is 12701412.

It is not a de Polignac number, because 21410721 - 2⁶ = 21410657 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a junction number, because it is equal to n+sod(n) for n = 21410694 and 21410703.

It is not an unprimeable number, because it can be changed into a prime (21410731) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17151 + ... + 18356.

It is an arithmetic number, because the mean of its divisors is an integer number (2615756).

Almost surely, 2^21410721 is an apocalyptic number.

It is an amenable number.

21410721 is a deficient number, since it is larger than the sum of its proper divisors (9978351).

21410721 is a wasteful number, since it uses less digits than its factorization.

21410721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35580 (or 35577 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 18.

The square root of 21410721 is about 4627.1720305171. The cubic root of 21410721 is about 277.6794651139.

The spelling of 21410721 in words is "twenty-one million, four hundred ten thousand, seven hundred twenty-one".