20721508 has 12 divisors (see below), whose sum is σ = 36877680. Its totient is φ = 10185032.

The previous prime is 20721497. The next prime is 20721509. The reversal of 20721508 is 80512702.

It is not an unprimeable number, because it can be changed into a prime (20721509) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 43666 + ... + 44137.

It is an arithmetic number, because the mean of its divisors is an integer number (3073140).

Almost surely, 2^20721508 is an apocalyptic number.

It is an amenable number.

20721508 is a deficient number, since it is larger than the sum of its proper divisors (16156172).

20721508 is a wasteful number, since it uses less digits than its factorization.

20721508 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87866 (or 87864 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 25.

The square root of 20721508 is about 4552.0883119729. The cubic root of 20721508 is about 274.6674017586.

The spelling of 20721508 in words is "twenty million, seven hundred twenty-one thousand, five hundred eight".