21139542 has 44 divisors (see below), whose sum is σ = 47829420. Its totient is φ = 7007148.

The previous prime is 21139513. The next prime is 21139577. The reversal of 21139542 is 24593112.

21139542 is a `hidden beast` number, since 2 + 113 + 9 + 542 = 666.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 21 ways as a sum of consecutive naturals, for example, 118009 + ... + 118187.

Almost surely, 2^21139542 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21139542, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23914710).

21139542 is an abundant number, since it is smaller than the sum of its proper divisors (26689878).

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

21139542 is an frugal number, since it uses more digits than its factorization.

21139542 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 211 (or 184 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 21139542 is about 4597.7757666072. The cubic root of 21139542 is about 276.5021576480.

The spelling of 21139542 in words is "twenty-one million, one hundred thirty-nine thousand, five hundred forty-two".