21979440 has 240 divisors, whose sum is σ = 87048000. Its totient is φ = 4967424.

The previous prime is 21979439. The next prime is 21979457. The reversal of 21979440 is 4497912.

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 21979395 and 21979404.

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 47 ways as a sum of consecutive naturals, for example, 246916 + ... + 247004.

It is an arithmetic number, because the mean of its divisors is an integer number (362700).

Almost surely, 2^21979440 is an apocalyptic number.

21979440 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 21979440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43524000).

21979440 is an abundant number, since it is smaller than the sum of its proper divisors (65068560).

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

21979440 is a wasteful number, since it uses less digits than its factorization.

21979440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129 (or 106 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21979440 is about 4688.2235441583. The cubic root of 21979440 is about 280.1166180893.

The spelling of 21979440 in words is "twenty-one million, nine hundred seventy-nine thousand, four hundred forty".