21089691 has 24 divisors (see below), whose sum is σ = 34935264. Its totient is φ = 12009600.

The previous prime is 21089683. The next prime is 21089711. The reversal of 21089691 is 19698012.

It is not a de Polignac number, because 21089691 - 2³ = 21089683 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21089611) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 34791 + ... + 35391.

It is an arithmetic number, because the mean of its divisors is an integer number (1455636).

Almost surely, 2^21089691 is an apocalyptic number.

21089691 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21089691 is a deficient number, since it is larger than the sum of its proper divisors (13845573).

21089691 is a wasteful number, since it uses less digits than its factorization.

21089691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1171 (or 1168 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21089691 is about 4592.3513585091. The cubic root of 21089691 is about 276.2846386136.

The spelling of 21089691 in words is "twenty-one million, eighty-nine thousand, six hundred ninety-one".