21556642 has 8 divisors (see below), whose sum is σ = 32504832. Its totient is φ = 10721700.

The previous prime is 21556627. The next prime is 21556643. The reversal of 21556642 is 24665512.

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

It is not an unprimeable number, because it can be changed into a prime (21556643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27834 + ... + 28597.

It is an arithmetic number, because the mean of its divisors is an integer number (4063104).

Almost surely, 2^21556642 is an apocalyptic number.

21556642 is a deficient number, since it is larger than the sum of its proper divisors (10948190).

21556642 is a wasteful number, since it uses less digits than its factorization.

21556642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56624.

The product of its digits is 14400, while the sum is 31.

The square root of 21556642 is about 4642.9130941684. The cubic root of 21556642 is about 278.3088625942.

The spelling of 21556642 in words is "twenty-one million, five hundred fifty-six thousand, six hundred forty-two".