21661116 has 12 divisors (see below), whose sum is σ = 50542632. Its totient is φ = 7220368.

The previous prime is 21661109. The next prime is 21661141. The reversal of 21661116 is 61116612.

It is a tau number, because it is divible by the number of its divisors (12).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 902535 + ... + 902558.

It is an arithmetic number, because the mean of its divisors is an integer number (4211886).

Almost surely, 2^21661116 is an apocalyptic number.

It is an amenable number.

21661116 is an abundant number, since it is smaller than the sum of its proper divisors (28881516).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661116 is a wasteful number, since it uses less digits than its factorization.

21661116 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1805100 (or 1805098 counting only the distinct ones).

The product of its digits is 432, while the sum is 24.

The square root of 21661116 is about 4654.1504058206. The cubic root of 21661116 is about 278.7577450307.

Adding to 21661116 its reverse (61116612), we get a palindrome (82777728).

The spelling of 21661116 in words is "twenty-one million, six hundred sixty-one thousand, one hundred sixteen".