21720853 has 8 divisors (see below), whose sum is σ = 27080640. Its totient is φ = 16925280.

The previous prime is 21720833. The next prime is 21720877. The reversal of 21720853 is 35802712.

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

It is a cyclic number.

It is not a de Polignac number, because 21720853 - 2⁵ = 21720821 is a prime.

It is a Duffinian number.

It is a plaindrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21720833) 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, 140968 + ... + 141121.

It is an arithmetic number, because the mean of its divisors is an integer number (3385080).

Almost surely, 2^21720853 is an apocalyptic number.

It is an amenable number.

21720853 is a deficient number, since it is larger than the sum of its proper divisors (5359787).

21720853 is a wasteful number, since it uses less digits than its factorization.

21720853 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 282107.

The product of its (nonzero) digits is 3360, while the sum is 28.

The square root of 21720853 is about 4660.5635925283. The cubic root of 21720853 is about 279.0137624194.

The spelling of 21720853 in words is "twenty-one million, seven hundred twenty thousand, eight hundred fifty-three".