21604380 has 48 divisors (see below), whose sum is σ = 69135360. Its totient is φ = 4938048.

The previous prime is 21604379. The next prime is 21604381. The reversal of 21604380 is 8340612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21604379) and next prime (21604381).

It is a self number, because there is not a number n which added to its sum of digits gives 21604380.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21604381) 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, 25300 + ... + 26139.

It is an arithmetic number, because the mean of its divisors is an integer number (1440320).

Almost surely, 2^21604380 is an apocalyptic number.

21604380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21604380 is an abundant number, since it is smaller than the sum of its proper divisors (47530980).

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

21604380 is a wasteful number, since it uses less digits than its factorization.

21604380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51458 (or 51456 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 21604380 is about 4648.0512045372. The cubic root of 21604380 is about 278.5141529659.

Adding to 21604380 its reverse (8340612), we get a palindrome (29944992).

The spelling of 21604380 in words is "twenty-one million, six hundred four thousand, three hundred eighty".