21691242 has 24 divisors (see below), whose sum is σ = 47361600. Its totient is φ = 7174440.

The previous prime is 21691223. The next prime is 21691247. The reversal of 21691242 is 24219612.

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 11 ways as a sum of consecutive naturals, for example, 2242 + ... + 6957.

It is an arithmetic number, because the mean of its divisors is an integer number (1973400).

Almost surely, 2^21691242 is an apocalyptic number.

21691242 is an abundant number, since it is smaller than the sum of its proper divisors (25670358).

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

21691242 is a wasteful number, since it uses less digits than its factorization.

21691242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9338 (or 9335 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21691242 is about 4657.3857473909. The cubic root of 21691242 is about 278.8869160550.

The spelling of 21691242 in words is "twenty-one million, six hundred ninety-one thousand, two hundred forty-two".