21720326 has 16 divisors (see below), whose sum is σ = 34236000. Its totient is φ = 10315008.

The previous prime is 21720317. The next prime is 21720371. The reversal of 21720326 is 62302712.

It is a Harshad number since it is a multiple of its sum of digits (23).

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 7 ways as a sum of consecutive naturals, for example, 5270 + ... + 8438.

It is an arithmetic number, because the mean of its divisors is an integer number (2139750).

Almost surely, 2^21720326 is an apocalyptic number.

21720326 is a deficient number, since it is larger than the sum of its proper divisors (12515674).

21720326 is a wasteful number, since it uses less digits than its factorization.

21720326 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3343.

The product of its (nonzero) digits is 1008, while the sum is 23.

The square root of 21720326 is about 4660.5070539588. The cubic root of 21720326 is about 279.0115058868.

The spelling of 21720326 in words is "twenty-one million, seven hundred twenty thousand, three hundred twenty-six".