21803993 has 4 divisors (see below), whose sum is σ = 21894708. Its totient is φ = 21713280.

The previous prime is 21803983. The next prime is 21804007. The reversal of 21803993 is 39930812.

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 16999129 + 4804864 = 4123^2 + 2192^2 .

It is a cyclic number.

It is not a de Polignac number, because 21803993 - 2²⁰ = 20755417 is a prime.

It is a super-2 number, since 2×21803993² = 950828221488098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21803933) 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, 44996 + ... + 45477.

It is an arithmetic number, because the mean of its divisors is an integer number (5473677).

Almost surely, 2^21803993 is an apocalyptic number.

It is an amenable number.

21803993 is a deficient number, since it is larger than the sum of its proper divisors (90715).

21803993 is an equidigital number, since it uses as much as digits as its factorization.

21803993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90714.

The product of its (nonzero) digits is 11664, while the sum is 35.

The square root of 21803993 is about 4669.4745957120. The cubic root of 21803993 is about 279.3692989476.

The spelling of 21803993 in words is "twenty-one million, eight hundred three thousand, nine hundred ninety-three".