21511116 has 96 divisors (see below), whose sum is σ = 64108800. Its totient is φ = 6168960.

The previous prime is 21511109. The next prime is 21511151. The reversal of 21511116 is 61111512.

It is a happy number.

It is a super-2 number, since 2×21511116² = 925456223130912, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22096 + ... + 23048.

It is an arithmetic number, because the mean of its divisors is an integer number (667800).

Almost surely, 2^21511116 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21511116, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32054400).

21511116 is an abundant number, since it is smaller than the sum of its proper divisors (42597684).

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

21511116 is a wasteful number, since it uses less digits than its factorization.

21511116 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 996 (or 988 counting only the distinct ones).

The product of its digits is 60, while the sum is 18.

The square root of 21511116 is about 4638.0077619599. The cubic root of 21511116 is about 278.1128020741.

Adding to 21511116 its reverse (61111512), we get a palindrome (82622628).

The spelling of 21511116 in words is "twenty-one million, five hundred eleven thousand, one hundred sixteen".