21229380 has 72 divisors (see below), whose sum is σ = 65520000. Its totient is φ = 5562432.

The previous prime is 21229361. The next prime is 21229387. The reversal of 21229380 is 8392212.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21229387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 9621 + ... + 11619.

It is an arithmetic number, because the mean of its divisors is an integer number (910000).

Almost surely, 2^21229380 is an apocalyptic number.

21229380 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 21229380, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32760000).

21229380 is an abundant number, since it is smaller than the sum of its proper divisors (44290620).

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

21229380 is a wasteful number, since it uses less digits than its factorization.

21229380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2073 (or 2068 counting only the distinct ones).

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

The square root of 21229380 is about 4607.5351328015. The cubic root of 21229380 is about 276.8932934493.

It can be divided in two parts, 21229 and 380, that added together give a square (21609 = 147²).

The spelling of 21229380 in words is "twenty-one million, two hundred twenty-nine thousand, three hundred eighty".