21278542 has 8 divisors (see below), whose sum is σ = 33305616. Its totient is φ = 10176672.

The previous prime is 21278501. The next prime is 21278557. The reversal of 21278542 is 24587212.

It is a happy number.

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

It is a congruent number.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 231243 + ... + 231334.

It is an arithmetic number, because the mean of its divisors is an integer number (4163202).

Almost surely, 2^21278542 is an apocalyptic number.

21278542 is a deficient number, since it is larger than the sum of its proper divisors (12027074).

21278542 is a wasteful number, since it uses less digits than its factorization.

21278542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 462602.

The product of its digits is 8960, while the sum is 31.

The square root of 21278542 is about 4612.8670043694. The cubic root of 21278542 is about 277.1068674956.

The spelling of 21278542 in words is "twenty-one million, two hundred seventy-eight thousand, five hundred forty-two".