21720446 has 8 divisors (see below), whose sum is σ = 35542584. Its totient is φ = 9872920.

The previous prime is 21720431. The next prime is 21720463. The reversal of 21720446 is 64402712.

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

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 493625 + ... + 493668.

It is an arithmetic number, because the mean of its divisors is an integer number (4442823).

Almost surely, 2^21720446 is an apocalyptic number.

21720446 is a deficient number, since it is larger than the sum of its proper divisors (13822138).

21720446 is a wasteful number, since it uses less digits than its factorization.

21720446 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 987306.

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21720446 is about 4660.5199280767. The cubic root of 21720446 is about 279.0120197114.

The spelling of 21720446 in words is "twenty-one million, seven hundred twenty thousand, four hundred forty-six".