21661115 has 16 divisors (see below), whose sum is σ = 30732480. Its totient is φ = 14340480.

The previous prime is 21661109. The next prime is 21661141. The reversal of 21661115 is 51116612.

It is not a de Polignac number, because 21661115 - 2⁶ = 21661051 is a prime.

It is an unprimeable number.

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, 9656 + ... + 11685.

It is an arithmetic number, because the mean of its divisors is an integer number (1920780).

Almost surely, 2^21661115 is an apocalyptic number.

21661115 is a deficient number, since it is larger than the sum of its proper divisors (9071365).

21661115 is a wasteful number, since it uses less digits than its factorization.

21661115 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21382.

The product of its digits is 360, while the sum is 23.

The square root of 21661115 is about 4654.1502983896. The cubic root of 21661115 is about 278.7577407410.

Adding to 21661115 its reverse (51116612), we get a palindrome (72777727).

The spelling of 21661115 in words is "twenty-one million, six hundred sixty-one thousand, one hundred fifteen".