21691359 has 12 divisors (see below), whose sum is σ = 31434936. Its totient is φ = 14413392.

The previous prime is 21691357. The next prime is 21691379. The reversal of 21691359 is 95319612.

21691359 is a `hidden beast` number, since 216 + 91 + 359 = 666.

It is not a de Polignac number, because 21691359 - 2¹ = 21691357 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21691357) 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, 949 + ... + 6654.

It is an arithmetic number, because the mean of its divisors is an integer number (2619578).

Almost surely, 2^21691359 is an apocalyptic number.

21691359 is a deficient number, since it is larger than the sum of its proper divisors (9743577).

21691359 is a wasteful number, since it uses less digits than its factorization.

21691359 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7926 (or 7923 counting only the distinct ones).

The product of its digits is 14580, while the sum is 36.

The square root of 21691359 is about 4657.3983080686. The cubic root of 21691359 is about 278.8874174818.

The spelling of 21691359 in words is "twenty-one million, six hundred ninety-one thousand, three hundred fifty-nine".