21988116 has 18 divisors (see below), whose sum is σ = 55581162. Its totient is φ = 7329360.

The previous prime is 21988103. The next prime is 21988133. The reversal of 21988116 is 61188912.

It can be written as a sum of positive squares in only one way, i.e., 21123216 + 864900 = 4596^2 + 930^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 610781 = 21988116 / (2 + 1 + 9 + 8 + 8 + 1 + 1 + 6).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 305355 + ... + 305426.

Almost surely, 2^21988116 is an apocalyptic number.

It is an amenable number.

21988116 is an abundant number, since it is smaller than the sum of its proper divisors (33593046).

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

21988116 is a wasteful number, since it uses less digits than its factorization.

21988116 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 610791 (or 610786 counting only the distinct ones).

The product of its digits is 6912, while the sum is 36.

The square root of 21988116 is about 4689.1487500398. The cubic root of 21988116 is about 280.1534702881.

Adding to 21988116 its product of digits (6912), we get a triangular number (21995028 = T₆₆₃₂).

The spelling of 21988116 in words is "twenty-one million, nine hundred eighty-eight thousand, one hundred sixteen".