21799440 has 240 divisors, whose sum is σ = 84088368. Its totient is φ = 5013504.

The previous prime is 21799439. The next prime is 21799447. The reversal of 21799440 is 4499712.

It can be written as a sum of positive squares in 8 ways, for example, as 121104 + 21678336 = 348^2 + 4656^2 .

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 = 21799395 and 21799404.

It is not an unprimeable number, because it can be changed into a prime (21799447) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 159052 + ... + 159188.

Almost surely, 2^21799440 is an apocalyptic number.

21799440 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 21799440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42044184).

21799440 is an abundant number, since it is smaller than the sum of its proper divisors (62288928).

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

21799440 is a wasteful number, since it uses less digits than its factorization.

21799440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 186 (or 177 counting only the distinct ones).

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

The square root of 21799440 is about 4668.9870421752. The cubic root of 21799440 is about 279.3498520973.

The spelling of 21799440 in words is "twenty-one million, seven hundred ninety-nine thousand, four hundred forty".