21720926 has 8 divisors (see below), whose sum is σ = 32634144. Its totient is φ = 10842880.

The previous prime is 21720911. The next prime is 21720929. The reversal of 21720926 is 62902712.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720929) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7190 + ... + 9753.

It is an arithmetic number, because the mean of its divisors is an integer number (4079268).

Almost surely, 2^21720926 is an apocalyptic number.

21720926 is a deficient number, since it is larger than the sum of its proper divisors (10913218).

21720926 is a wasteful number, since it uses less digits than its factorization.

21720926 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17586.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 21720926 is about 4660.5714241925. The cubic root of 21720926 is about 279.0140749913.

The spelling of 21720926 in words is "twenty-one million, seven hundred twenty thousand, nine hundred twenty-six".