21691244 has 12 divisors (see below), whose sum is σ = 37993368. Its totient is φ = 10836000.

The previous prime is 21691223. The next prime is 21691247. The reversal of 21691244 is 44219612.

It is not an unprimeable number, because it can be changed into a prime (21691247) 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, 5699 + ... + 8709.

It is an arithmetic number, because the mean of its divisors is an integer number (3166114).

Almost surely, 2^21691244 is an apocalyptic number.

It is an amenable number.

21691244 is a deficient number, since it is larger than the sum of its proper divisors (16302124).

21691244 is a wasteful number, since it uses less digits than its factorization.

21691244 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4816 (or 4814 counting only the distinct ones).

The product of its digits is 3456, while the sum is 29.

The square root of 21691244 is about 4657.3859621036. The cubic root of 21691244 is about 278.8869246264.

The spelling of 21691244 in words is "twenty-one million, six hundred ninety-one thousand, two hundred forty-four".