21791688 has 32 divisors (see below), whose sum is σ = 57684960. Its totient is φ = 6836480.

The previous prime is 21791687. The next prime is 21791699. The reversal of 21791688 is 88619712.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21791681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26298 + ... + 27113.

It is an arithmetic number, because the mean of its divisors is an integer number (1802655).

Almost surely, 2^21791688 is an apocalyptic number.

It is an amenable number.

21791688 is an abundant number, since it is smaller than the sum of its proper divisors (35893272).

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

21791688 is a wasteful number, since it uses less digits than its factorization.

21791688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53437 (or 53433 counting only the distinct ones).

The product of its digits is 48384, while the sum is 42.

The square root of 21791688 is about 4668.1568097055. The cubic root of 21791688 is about 279.3167353935.

The spelling of 21791688 in words is "twenty-one million, seven hundred ninety-one thousand, six hundred eighty-eight".