21813903 has 12 divisors (see below), whose sum is σ = 31634928. Its totient is φ = 14484480.

The previous prime is 21813877. The next prime is 21813931. The reversal of 21813903 is 30931812.

It is not a de Polignac number, because 21813903 - 2¹⁶ = 21748367 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21813973) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2403 + ... + 7028.

It is an arithmetic number, because the mean of its divisors is an integer number (2636244).

Almost surely, 2^21813903 is an apocalyptic number.

21813903 is a deficient number, since it is larger than the sum of its proper divisors (9821025).

21813903 is a wasteful number, since it uses less digits than its factorization.

21813903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9694 (or 9691 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21813903 is about 4670.5356223885. The cubic root of 21813903 is about 279.4116173496.

It can be divided in two parts, 2181 and 3903, that added together give a square (6084 = 78²).

The spelling of 21813903 in words is "twenty-one million, eight hundred thirteen thousand, nine hundred three".