21721116 has 24 divisors (see below), whose sum is σ = 52431120. Its totient is φ = 6990592.

The previous prime is 21721081. The next prime is 21721127. The reversal of 21721116 is 61112712.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21721092 and 21721101.

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 7 ways as a sum of consecutive naturals, for example, 30861 + ... + 31556.

It is an arithmetic number, because the mean of its divisors is an integer number (2184630).

Almost surely, 2^21721116 is an apocalyptic number.

It is an amenable number.

21721116 is an abundant number, since it is smaller than the sum of its proper divisors (30710004).

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

21721116 is a wasteful number, since it uses less digits than its factorization.

21721116 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 62453 (or 62451 counting only the distinct ones).

The product of its digits is 168, while the sum is 21.

The square root of 21721116 is about 4660.5918079145. The cubic root of 21721116 is about 279.0148885312.

Adding to 21721116 its reverse (61112712), we get a palindrome (82833828).

The spelling of 21721116 in words is "twenty-one million, seven hundred twenty-one thousand, one hundred sixteen".