21720760 has 16 divisors (see below), whose sum is σ = 48871800. Its totient is φ = 8688288.

The previous prime is 21720749. The next prime is 21720779. The reversal of 21720760 is 6702712.

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, 271470 + ... + 271549.

Almost surely, 2^21720760 is an apocalyptic number.

21720760 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21720760 is an abundant number, since it is smaller than the sum of its proper divisors (27151040).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21720760 is a wasteful number, since it uses less digits than its factorization.

21720760 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 543030 (or 543026 counting only the distinct ones).

The product of its (nonzero) digits is 1176, while the sum is 25.

The square root of 21720760 is about 4660.5536151835. The cubic root of 21720760 is about 279.0133642104.

The spelling of 21720760 in words is "twenty-one million, seven hundred twenty thousand, seven hundred sixty".