21090384 has 150 divisors (see below), whose sum is σ = 69985786. Its totient is φ = 5927040.

The previous prime is 21090373. The next prime is 21090397. The reversal of 21090384 is 48309012.

21090384 = 50³ + 51³ + ... + 97³.

It can be written as a sum of positive squares in only one way, i.e., 12446784 + 8643600 = 3528^2 + 2940^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 345714 + ... + 345774.

Almost surely, 2^21090384 is an apocalyptic number.

21090384 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21090384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34992893).

21090384 is an abundant number, since it is smaller than the sum of its proper divisors (48895402).

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

21090384 is an equidigital number, since it uses as much as digits as its factorization.

21090384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 103 (or 73 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 21090384 is about 4592.4268094331. The cubic root of 21090384 is about 276.2876647866.

Adding to 21090384 its reverse (48309012), we get a palindrome (69399396).

The spelling of 21090384 in words is "twenty-one million, ninety thousand, three hundred eighty-four".