21639830 has 8 divisors (see below), whose sum is σ = 38951712. Its totient is φ = 8655928.

The previous prime is 21639823. The next prime is 21639833. The reversal of 21639830 is 3893612.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639833) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1081982 + ... + 1082001.

It is an arithmetic number, because the mean of its divisors is an integer number (4868964).

Almost surely, 2^21639830 is an apocalyptic number.

21639830 is a deficient number, since it is larger than the sum of its proper divisors (17311882).

21639830 is a wasteful number, since it uses less digits than its factorization.

21639830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2163990.

The product of its (nonzero) digits is 7776, while the sum is 32.

The square root of 21639830 is about 4651.8630676322. The cubic root of 21639830 is about 278.6664049839. Note that the first 3 decimals are identical.

The spelling of 21639830 in words is "twenty-one million, six hundred thirty-nine thousand, eight hundred thirty".