20721560 has 32 divisors (see below), whose sum is σ = 46753200. Its totient is φ = 8265600.

The previous prime is 20721553. The next prime is 20721583. The reversal of 20721560 is 6512702.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27671 + ... + 28409.

Almost surely, 2^20721560 is an apocalyptic number.

20721560 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20721560 is an abundant number, since it is smaller than the sum of its proper divisors (26031640).

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

20721560 is a wasteful number, since it uses less digits than its factorization.

20721560 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1451 (or 1447 counting only the distinct ones).

The product of its (nonzero) digits is 840, while the sum is 23.

The square root of 20721560 is about 4552.0940236335. The cubic root of 20721560 is about 274.6676315149.

The spelling of 20721560 in words is "twenty million, seven hundred twenty-one thousand, five hundred sixty".