21316638 has 32 divisors (see below), whose sum is σ = 49916160. Its totient is φ = 5941440.

The previous prime is 21316619. The next prime is 21316639. The reversal of 21316638 is 83661312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21316639) 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, 4468 + ... + 7911.

It is an arithmetic number, because the mean of its divisors is an integer number (1559880).

Almost surely, 2^21316638 is an apocalyptic number.

21316638 is an abundant number, since it is smaller than the sum of its proper divisors (28599522).

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

21316638 is a wasteful number, since it uses less digits than its factorization.

21316638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12432.

The product of its digits is 5184, while the sum is 30.

The square root of 21316638 is about 4616.9944769298. The cubic root of 21316638 is about 277.2721414987.

The spelling of 21316638 in words is "twenty-one million, three hundred sixteen thousand, six hundred thirty-eight".