21726691 has 16 divisors (see below), whose sum is σ = 26081280. Its totient is φ = 17706240.

The previous prime is 21726613. The next prime is 21726701. The reversal of 21726691 is 19662712.

It is a cyclic number.

It is not a de Polignac number, because 21726691 - 2¹⁹ = 21202403 is a prime.

It is a Duffinian number.

21726691 is a modest number, since divided by 26691 gives 217 as remainder.

It is not an unprimeable number, because it can be changed into a prime (21726611) 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 15 ways as a sum of consecutive naturals, for example, 11955 + ... + 13651.

It is an arithmetic number, because the mean of its divisors is an integer number (1630080).

Almost surely, 2^21726691 is an apocalyptic number.

21726691 is a deficient number, since it is larger than the sum of its proper divisors (4354589).

21726691 is a wasteful number, since it uses less digits than its factorization.

21726691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1794.

The product of its digits is 9072, while the sum is 34.

The square root of 21726691 is about 4661.1898695505. The cubic root of 21726691 is about 279.0387573929.

The spelling of 21726691 in words is "twenty-one million, seven hundred twenty-six thousand, six hundred ninety-one".