20918421 has 6 divisors (see below), whose sum is σ = 30215510. Its totient is φ = 13945608.

The previous prime is 20918399. The next prime is 20918441. The reversal of 20918421 is 12481902.

It can be written as a sum of positive squares in only one way, i.e., 16695396 + 4223025 = 4086^2 + 2055^2 .

It is not a de Polignac number, because 20918421 - 2⁵ = 20918389 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20918441) 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 5 ways as a sum of consecutive naturals, for example, 1162126 + ... + 1162143.

Almost surely, 2^20918421 is an apocalyptic number.

It is an amenable number.

20918421 is a deficient number, since it is larger than the sum of its proper divisors (9297089).

20918421 is a wasteful number, since it uses less digits than its factorization.

20918421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2324275 (or 2324272 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 20918421 is about 4573.6660350314. Note that the first 3 decimals coincide. The cubic root of 20918421 is about 275.5346996213.

The spelling of 20918421 in words is "twenty million, nine hundred eighteen thousand, four hundred twenty-one".