20508721 has 8 divisors (see below), whose sum is σ = 21384000. Its totient is φ = 19651632.

The previous prime is 20508707. The next prime is 20508731. The reversal of 20508721 is 12780502.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20508721 - 2¹⁵ = 20475953 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20508731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2221 + ... + 6778.

It is an arithmetic number, because the mean of its divisors is an integer number (2673000).

Almost surely, 2^20508721 is an apocalyptic number.

It is an amenable number.

20508721 is a deficient number, since it is larger than the sum of its proper divisors (875279).

20508721 is an equidigital number, since it uses as much as digits as its factorization.

20508721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9095.

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

The square root of 20508721 is about 4528.6555400030. The cubic root of 20508721 is about 273.7239881319.

The spelling of 20508721 in words is "twenty million, five hundred eight thousand, seven hundred twenty-one".