21903816 has 64 divisors (see below), whose sum is σ = 61819200. Its totient is φ = 6406400.

The previous prime is 21903811. The next prime is 21903821. The reversal of 21903816 is 61830912.

It is an interprime number because it is at equal distance from previous prime (21903811) and next prime (21903821).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21903811) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6226 + ... + 9086.

It is an arithmetic number, because the mean of its divisors is an integer number (965925).

Almost surely, 2^21903816 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 21903816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30909600).

21903816 is an abundant number, since it is smaller than the sum of its proper divisors (39915384).

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

21903816 is a wasteful number, since it uses less digits than its factorization.

21903816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2910 (or 2906 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 30.

The square root of 21903816 is about 4680.1512796062. The cubic root of 21903816 is about 279.7949859812.

It can be divided in two parts, 2190 and 3816, that added together give a palindrome (6006).

The spelling of 21903816 in words is "twenty-one million, nine hundred three thousand, eight hundred sixteen".