21278442 has 16 divisors (see below), whose sum is σ = 44796960. Its totient is φ = 6719472.

The previous prime is 21278419. The next prime is 21278449. The reversal of 21278442 is 24487212.

It is not an unprimeable number, because it can be changed into a prime (21278449) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 93213 + ... + 93440.

It is an arithmetic number, because the mean of its divisors is an integer number (2799810).

Almost surely, 2^21278442 is an apocalyptic number.

21278442 is an abundant number, since it is smaller than the sum of its proper divisors (23518518).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21278442 is a wasteful number, since it uses less digits than its factorization.

21278442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 186677.

The product of its digits is 7168, while the sum is 30.

The square root of 21278442 is about 4612.8561651107. The cubic root of 21278442 is about 277.1064334005.

The spelling of 21278442 in words is "twenty-one million, two hundred seventy-eight thousand, four hundred forty-two".