21388080 has 160 divisors (see below), whose sum is σ = 78566400. Its totient is φ = 4709376.

The previous prime is 21388049. The next prime is 21388099. The reversal of 21388080 is 8088312.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 31 ways as a sum of consecutive naturals, for example, 48501 + ... + 48939.

It is an arithmetic number, because the mean of its divisors is an integer number (491040).

Almost surely, 2^21388080 is an apocalyptic number.

21388080 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 21388080, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39283200).

21388080 is an abundant number, since it is smaller than the sum of its proper divisors (57178320).

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

21388080 is a wasteful number, since it uses less digits than its factorization.

21388080 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 491 (or 485 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 21388080 is about 4624.7248566807. The cubic root of 21388080 is about 277.5815522017.

The spelling of 21388080 in words is "twenty-one million, three hundred eighty-eight thousand, eighty".