21779440 has 40 divisors (see below), whose sum is σ = 51478848. Its totient is φ = 8567040.

The previous prime is 21779423. The next prime is 21779447. The reversal of 21779440 is 4497712.

It is a tau number, because it is divible by the number of its divisors (40).

It is a junction number, because it is equal to n+sod(n) for n = 21779396 and 21779405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21779447) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2649 + ... + 7111.

Almost surely, 2^21779440 is an apocalyptic number.

21779440 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 21779440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25739424).

21779440 is an abundant number, since it is smaller than the sum of its proper divisors (29699408).

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

21779440 is a wasteful number, since it uses less digits than its factorization.

21779440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4537 (or 4531 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 34.

The square root of 21779440 is about 4666.8447585065. The cubic root of 21779440 is about 279.2643956740.

The spelling of 21779440 in words is "twenty-one million, seven hundred seventy-nine thousand, four hundred forty".