21991706 has 8 divisors (see below), whose sum is σ = 35986464. Its totient is φ = 9996220.

The previous prime is 21991699. The next prime is 21991733. The reversal of 21991706 is 60719912.

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

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, 499790 + ... + 499833.

It is an arithmetic number, because the mean of its divisors is an integer number (4498308).

Almost surely, 2^21991706 is an apocalyptic number.

21991706 is a deficient number, since it is larger than the sum of its proper divisors (13994758).

21991706 is a wasteful number, since it uses less digits than its factorization.

21991706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 999636.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 21991706 is about 4689.5315331065. The cubic root of 21991706 is about 280.1687163453.

The spelling of 21991706 in words is "twenty-one million, nine hundred ninety-one thousand, seven hundred six".