21721366 has 8 divisors (see below), whose sum is σ = 32994720. Its totient is φ = 10723128.

The previous prime is 21721303. The next prime is 21721373. The reversal of 21721366 is 66312712.

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

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, 68581 + ... + 68896.

It is an arithmetic number, because the mean of its divisors is an integer number (4124340).

Almost surely, 2^21721366 is an apocalyptic number.

21721366 is a deficient number, since it is larger than the sum of its proper divisors (11273354).

21721366 is a wasteful number, since it uses less digits than its factorization.

21721366 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 137558.

The product of its digits is 3024, while the sum is 28.

The square root of 21721366 is about 4660.6186284655. The cubic root of 21721366 is about 279.0159589712.

The spelling of 21721366 in words is "twenty-one million, seven hundred twenty-one thousand, three hundred sixty-six".