21556542 has 32 divisors (see below), whose sum is σ = 49450752. Its totient is φ = 6136704.

The previous prime is 21556519. The next prime is 21556547. The reversal of 21556542 is 24565512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21556547) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13393 + ... + 14915.

It is an arithmetic number, because the mean of its divisors is an integer number (1545336).

Almost surely, 2^21556542 is an apocalyptic number.

21556542 is an abundant number, since it is smaller than the sum of its proper divisors (27894210).

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

21556542 is a wasteful number, since it uses less digits than its factorization.

21556542 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1872.

The product of its digits is 12000, while the sum is 30.

The square root of 21556542 is about 4642.9023250549. The cubic root of 21556542 is about 278.3084322407.

The spelling of 21556542 in words is "twenty-one million, five hundred fifty-six thousand, five hundred forty-two".