20721393 has 32 divisors (see below), whose sum is σ = 38277120. Its totient is φ = 10763280.

The previous prime is 20721391. The next prime is 20721397. The reversal of 20721393 is 39312702.

It is not a de Polignac number, because 20721393 - 2¹ = 20721391 is a prime.

It is a super-2 number, since 2×20721393² = 858752255720898, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (20721391) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2905 + ... + 7062.

It is an arithmetic number, because the mean of its divisors is an integer number (1196160).

Almost surely, 2^20721393 is an apocalyptic number.

It is an amenable number.

20721393 is a deficient number, since it is larger than the sum of its proper divisors (17555727).

20721393 is a wasteful number, since it uses less digits than its factorization.

20721393 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9994 (or 9988 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 20721393 is about 4552.0756803902. The cubic root of 20721393 is about 274.6668936423. Note that the first 3 decimals are identical.

The spelling of 20721393 in words is "twenty million, seven hundred twenty-one thousand, three hundred ninety-three".