21755420 has 48 divisors (see below), whose sum is σ = 47966688. Its totient is φ = 8279040.

The previous prime is 21755413. The next prime is 21755429. The reversal of 21755420 is 2455712.

It is a self number, because there is not a number n which added to its sum of digits gives 21755420.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21755429) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34952 + ... + 35568.

It is an arithmetic number, because the mean of its divisors is an integer number (999306).

Almost surely, 2^21755420 is an apocalyptic number.

21755420 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 21755420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23983344).

21755420 is an abundant number, since it is smaller than the sum of its proper divisors (26211268).

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

21755420 is a wasteful number, since it uses less digits than its factorization.

21755420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 710 (or 708 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21755420 is about 4664.2705753419. The cubic root of 21755420 is about 279.1616933348.

The spelling of 21755420 in words is "twenty-one million, seven hundred fifty-five thousand, four hundred twenty".