21873321 has 30 divisors (see below), whose sum is σ = 33883146. Its totient is φ = 14061600.

The previous prime is 21873311. The next prime is 21873331. The reversal of 21873321 is 12337812.

It is an interprime number because it is at equal distance from previous prime (21873311) and next prime (21873331).

It can be written as a sum of positive squares in only one way, i.e., 19927296 + 1946025 = 4464^2 + 1395^2 .

It is not a de Polignac number, because 21873321 - 2¹¹ = 21871273 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21873311) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 77701 + ... + 77981.

Almost surely, 2^21873321 is an apocalyptic number.

It is an amenable number.

21873321 is a deficient number, since it is larger than the sum of its proper divisors (12009825).

21873321 is an equidigital number, since it uses as much as digits as its factorization.

21873321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 355 (or 315 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21873321 is about 4676.8922373730. The cubic root of 21873321 is about 279.6650799897.

The spelling of 21873321 in words is "twenty-one million, eight hundred seventy-three thousand, three hundred twenty-one".