21056240 has 40 divisors (see below), whose sum is σ = 50102448. Its totient is φ = 8225280.

The previous prime is 21056227. The next prime is 21056249. The reversal of 21056240 is 4265012.

It is a happy number.

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

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21056249) 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, 380 + ... + 6500.

Almost surely, 2^21056240 is an apocalyptic number.

21056240 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 21056240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25051224).

21056240 is an abundant number, since it is smaller than the sum of its proper divisors (29046208).

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

21056240 is a wasteful number, since it uses less digits than its factorization.

21056240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6177 (or 6171 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 21056240 is about 4588.7078791311. The cubic root of 21056240 is about 276.1384868264.

The spelling of 21056240 in words is "twenty-one million, fifty-six thousand, two hundred forty".