21816916 has 24 divisors (see below), whose sum is σ = 44102016. Its totient is φ = 9333120.

The previous prime is 21816889. The next prime is 21816917. The reversal of 21816916 is 61961812.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21816917) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13836 + ... + 15331.

It is an arithmetic number, because the mean of its divisors is an integer number (1837584).

Almost surely, 2^21816916 is an apocalyptic number.

It is an amenable number.

21816916 is an abundant number, since it is smaller than the sum of its proper divisors (22285100).

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

21816916 is a wasteful number, since it uses less digits than its factorization.

21816916 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29199 (or 29197 counting only the distinct ones).

The product of its digits is 5184, while the sum is 34.

The square root of 21816916 is about 4670.8581652626. The cubic root of 21816916 is about 279.4244811402.

Subtracting 21816916 from its reverse (61961812), we obtain a square (40144896 = 6336²).

The spelling of 21816916 in words is "twenty-one million, eight hundred sixteen thousand, nine hundred sixteen".