21720633 has 16 divisors (see below), whose sum is σ = 32330496. Its totient is φ = 12857040.

The previous prime is 21720631. The next prime is 21720649. The reversal of 21720633 is 33602712.

It is not a de Polignac number, because 21720633 - 2¹ = 21720631 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21720631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6235 + ... + 9072.

It is an arithmetic number, because the mean of its divisors is an integer number (2020656).

Almost surely, 2^21720633 is an apocalyptic number.

It is an amenable number.

21720633 is a deficient number, since it is larger than the sum of its proper divisors (10609863).

21720633 is a wasteful number, since it uses less digits than its factorization.

21720633 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15364.

The product of its (nonzero) digits is 1512, while the sum is 24.

The square root of 21720633 is about 4660.5399901728. The cubic root of 21720633 is about 279.0128204178.

The spelling of 21720633 in words is "twenty-one million, seven hundred twenty thousand, six hundred thirty-three".