21579740 has 96 divisors (see below), whose sum is σ = 56899584. Its totient is φ = 6693120.

The previous prime is 21579737. The next prime is 21579791. The reversal of 21579740 is 4797512.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 21579740.

It is a congruent number.

It is an unprimeable number.

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 31 ways as a sum of consecutive naturals, for example, 129137 + ... + 129303.

It is an arithmetic number, because the mean of its divisors is an integer number (592704).

Almost surely, 2^21579740 is an apocalyptic number.

21579740 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 21579740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28449792).

21579740 is an abundant number, since it is smaller than the sum of its proper divisors (35319844).

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

21579740 is a wasteful number, since it uses less digits than its factorization.

21579740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267 (or 265 counting only the distinct ones).

The product of its (nonzero) digits is 17640, while the sum is 35.

The square root of 21579740 is about 4645.3998751453. The cubic root of 21579740 is about 278.4082300106.

The spelling of 21579740 in words is "twenty-one million, five hundred seventy-nine thousand, seven hundred forty".