21129380 has 12 divisors (see below), whose sum is σ = 44371740. Its totient is φ = 8451744.

The previous prime is 21129379. The next prime is 21129403. The reversal of 21129380 is 8392112.

It can be written as a sum of positive squares in 2 ways, for example, as 13957696 + 7171684 = 3736^2 + 2678^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 528215 + ... + 528254.

It is an arithmetic number, because the mean of its divisors is an integer number (3697645).

Almost surely, 2^21129380 is an apocalyptic number.

21129380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21129380 is an abundant number, since it is smaller than the sum of its proper divisors (23242360).

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

21129380 is a wasteful number, since it uses less digits than its factorization.

21129380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1056478 (or 1056476 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 21129380 is about 4596.6705342019. The cubic root of 21129380 is about 276.4578447157.

The spelling of 21129380 in words is "twenty-one million, one hundred twenty-nine thousand, three hundred eighty".