21115380 has 192 divisors, whose sum is σ = 73156608. Its totient is φ = 4477440.

The previous prime is 21115379. The next prime is 21115417. The reversal of 21115380 is 8351112.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 197287 + ... + 197393.

It is an arithmetic number, because the mean of its divisors is an integer number (381024).

Almost surely, 2^21115380 is an apocalyptic number.

21115380 is a gapful number since it is divisible by the number (20) 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 21115380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36578304).

21115380 is an abundant number, since it is smaller than the sum of its proper divisors (52041228).

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

21115380 is a wasteful number, since it uses less digits than its factorization.

21115380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 166 (or 164 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 21.

The square root of 21115380 is about 4595.1474405072. The cubic root of 21115380 is about 276.3967723295.

Adding to 21115380 its reverse (8351112), we get a palindrome (29466492).

The spelling of 21115380 in words is "twenty-one million, one hundred fifteen thousand, three hundred eighty".