21939906 has 8 divisors (see below), whose sum is σ = 43879824. Its totient is φ = 7313300.

The previous prime is 21939881. The next prime is 21939919. The reversal of 21939906 is 60993912.

It is a happy number.

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

21939906 is an admirable number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1828320 + ... + 1828331.

It is an arithmetic number, because the mean of its divisors is an integer number (5484978).

Almost surely, 2^21939906 is an apocalyptic number.

21939906 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.

21939906 is a wasteful number, since it uses less digits than its factorization.

21939906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3656656.

The product of its (nonzero) digits is 26244, while the sum is 39.

The square root of 21939906 is about 4684.0053373155. The cubic root of 21939906 is about 279.9485704861.

The spelling of 21939906 in words is "twenty-one million, nine hundred thirty-nine thousand, nine hundred six".