21978333 has 24 divisors (see below), whose sum is σ = 35119448. Its totient is φ = 13156992.

The previous prime is 21978311. The next prime is 21978343. The reversal of 21978333 is 33387912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 9847044 + 12131289 = 3138^2 + 3483^2 .

It is not a de Polignac number, because 21978333 - 2⁵ = 21978301 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21978343) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1791 + ... + 6867.

Almost surely, 2^21978333 is an apocalyptic number.

It is an amenable number.

21978333 is a deficient number, since it is larger than the sum of its proper divisors (13141115).

21978333 is a wasteful number, since it uses less digits than its factorization.

21978333 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5133 (or 5130 counting only the distinct ones).

The product of its digits is 27216, while the sum is 36.

The square root of 21978333 is about 4688.1054808952. The cubic root of 21978333 is about 280.1119152958. Note that the first 3 decimals are identical.

The spelling of 21978333 in words is "twenty-one million, nine hundred seventy-eight thousand, three hundred thirty-three".