20736421 has 4 divisors (see below), whose sum is σ = 21451500. Its totient is φ = 20021344.

The previous prime is 20736407. The next prime is 20736431. The reversal of 20736421 is 12463702.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12463702 = 2 ⋅6231851.

It can be written as a sum of positive squares in 2 ways, for example, as 17313921 + 3422500 = 4161^2 + 1850^2 .

It is a cyclic number.

It is not a de Polignac number, because 20736421 - 2¹³ = 20728229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20736431) 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, 357496 + ... + 357553.

It is an arithmetic number, because the mean of its divisors is an integer number (5362875).

Almost surely, 2^20736421 is an apocalyptic number.

It is an amenable number.

20736421 is a deficient number, since it is larger than the sum of its proper divisors (715079).

20736421 is an equidigital number, since it uses as much as digits as its factorization.

20736421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 715078.

The product of its (nonzero) digits is 2016, while the sum is 25.

The square root of 20736421 is about 4553.7260567584. The cubic root of 20736421 is about 274.7332774776.

The spelling of 20736421 in words is "twenty million, seven hundred thirty-six thousand, four hundred twenty-one".