21609642 has 8 divisors (see below), whose sum is σ = 43219296. Its totient is φ = 7203212.

The previous prime is 21609641. The next prime is 21609649. The reversal of 21609642 is 24690612.

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

21609642 is an admirable number.

It is not an unprimeable number, because it can be changed into a prime (21609641) 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 3 ways as a sum of consecutive naturals, for example, 1800798 + ... + 1800809.

It is an arithmetic number, because the mean of its divisors is an integer number (5402412).

Almost surely, 2^21609642 is an apocalyptic number.

21609642 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21609642 is a wasteful number, since it uses less digits than its factorization.

21609642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3601612.

The product of its (nonzero) digits is 5184, while the sum is 30.

The square root of 21609642 is about 4648.6172137529. The cubic root of 21609642 is about 278.5367629260.

The spelling of 21609642 in words is "twenty-one million, six hundred nine thousand, six hundred forty-two".