21278433 has 8 divisors (see below), whose sum is σ = 30950496. Its totient is φ = 12896000.

The previous prime is 21278419. The next prime is 21278449. The reversal of 21278433 is 33487212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21278433 - 2⁴ = 21278417 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21278433.

It is not an unprimeable number, because it can be changed into a prime (21278483) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 322368 + ... + 322433.

It is an arithmetic number, because the mean of its divisors is an integer number (3868812).

Almost surely, 2^21278433 is an apocalyptic number.

It is an amenable number.

21278433 is a deficient number, since it is larger than the sum of its proper divisors (9672063).

21278433 is a wasteful number, since it uses less digits than its factorization.

21278433 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 644815.

The product of its digits is 8064, while the sum is 30.

The square root of 21278433 is about 4612.8551895762. The cubic root of 21278433 is about 277.1063943319.

The spelling of 21278433 in words is "twenty-one million, two hundred seventy-eight thousand, four hundred thirty-three".