20163721 has 4 divisors (see below), whose sum is σ = 20223892. Its totient is φ = 20103552.

The previous prime is 20163707. The next prime is 20163739. The reversal of 20163721 is 12736102.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13220496 + 6943225 = 3636^2 + 2635^2 .

It is a cyclic number.

It is not a de Polignac number, because 20163721 - 2⁷ = 20163593 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20163692 and 20163701.

It is not an unprimeable number, because it can be changed into a prime (20163701) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 29580 + ... + 30253.

It is an arithmetic number, because the mean of its divisors is an integer number (5055973).

Almost surely, 2^20163721 is an apocalyptic number.

It is an amenable number.

20163721 is a deficient number, since it is larger than the sum of its proper divisors (60171).

20163721 is an equidigital number, since it uses as much as digits as its factorization.

20163721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60170.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 20163721 is about 4490.4032112941. The cubic root of 20163721 is about 272.1804283347.

Adding to 20163721 its reverse (12736102), we get a palindrome (32899823).

The spelling of 20163721 in words is "twenty million, one hundred sixty-three thousand, seven hundred twenty-one".