21720353 has 8 divisors (see below), whose sum is σ = 22208256. Its totient is φ = 21238000.

The previous prime is 21720317. The next prime is 21720371. The reversal of 21720353 is 35302712.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21720353 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21720053) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7088 + ... + 9678.

It is an arithmetic number, because the mean of its divisors is an integer number (2776032).

Almost surely, 2^21720353 is an apocalyptic number.

It is an amenable number.

21720353 is a deficient number, since it is larger than the sum of its proper divisors (487903).

21720353 is a wasteful number, since it uses less digits than its factorization.

21720353 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2775.

The product of its (nonzero) digits is 1260, while the sum is 23.

The square root of 21720353 is about 4660.5099506384. The cubic root of 21720353 is about 279.0116214975.

The spelling of 21720353 in words is "twenty-one million, seven hundred twenty thousand, three hundred fifty-three".