20921747 has 24 divisors (see below), whose sum is σ = 27847008. Its totient is φ = 15333120.

The previous prime is 20921741. The next prime is 20921773. The reversal of 20921747 is 74712902.

It is not a de Polignac number, because 20921747 - 2¹⁰ = 20920723 is a prime.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (20921741) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13673 + ... + 15125.

It is an arithmetic number, because the mean of its divisors is an integer number (1160292).

Almost surely, 2^20921747 is an apocalyptic number.

20921747 is a deficient number, since it is larger than the sum of its proper divisors (6925261).

20921747 is a wasteful number, since it uses less digits than its factorization.

20921747 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1499 (or 1488 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 20921747 is about 4574.0296238656. The cubic root of 20921747 is about 275.5493020594.

The spelling of 20921747 in words is "twenty million, nine hundred twenty-one thousand, seven hundred forty-seven".