21591115 has 24 divisors (see below), whose sum is σ = 32462640. Its totient is φ = 13664448.

The previous prime is 21591113. The next prime is 21591127. The reversal of 21591115 is 51119512.

It is a happy number.

It is not a de Polignac number, because 21591115 - 2¹ = 21591113 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21591115.

It is not an unprimeable number, because it can be changed into a prime (21591113) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 205 + ... + 6574.

It is an arithmetic number, because the mean of its divisors is an integer number (1352610).

Almost surely, 2^21591115 is an apocalyptic number.

21591115 is a deficient number, since it is larger than the sum of its proper divisors (10871525).

21591115 is a wasteful number, since it uses less digits than its factorization.

21591115 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6811 (or 6804 counting only the distinct ones).

The product of its digits is 450, while the sum is 25.

The square root of 21591115 is about 4646.6240433244. The cubic root of 21591115 is about 278.4571391161.

The spelling of 21591115 in words is "twenty-one million, five hundred ninety-one thousand, one hundred fifteen".