21789691 has 16 divisors (see below), whose sum is σ = 27802368. Its totient is φ = 16581600.

The previous prime is 21789689. The next prime is 21789709. The reversal of 21789691 is 19698712.

It is not a de Polignac number, because 21789691 - 2¹ = 21789689 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (43).

It is not an unprimeable number, because it can be changed into a prime (21789641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21 + ... + 6601.

It is an arithmetic number, because the mean of its divisors is an integer number (1737648).

Almost surely, 2^21789691 is an apocalyptic number.

21789691 is a deficient number, since it is larger than the sum of its proper divisors (6012677).

21789691 is a wasteful number, since it uses less digits than its factorization.

21789691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6642.

The product of its digits is 54432, while the sum is 43.

The square root of 21789691 is about 4667.9429088197. The cubic root of 21789691 is about 279.3082028961.

The spelling of 21789691 in words is "twenty-one million, seven hundred eighty-nine thousand, six hundred ninety-one".