21563140 has 24 divisors (see below), whose sum is σ = 47947032. Its totient is φ = 8117760.

The previous prime is 21563137. The next prime is 21563147. The reversal of 21563140 is 4136512.

It can be written as a sum of positive squares in 4 ways, for example, as 1617984 + 19945156 = 1272^2 + 4466^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21563147) 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, 31371 + ... + 32050.

It is an arithmetic number, because the mean of its divisors is an integer number (1997793).

Almost surely, 2^21563140 is an apocalyptic number.

21563140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21563140 is an abundant number, since it is smaller than the sum of its proper divisors (26383892).

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

21563140 is a wasteful number, since it uses less digits than its factorization.

21563140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63447 (or 63445 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 21563140 is about 4643.6128176238. The cubic root of 21563140 is about 278.3368241123.

Adding to 21563140 its reverse (4136512), we get a palindrome (25699652).

The spelling of 21563140 in words is "twenty-one million, five hundred sixty-three thousand, one hundred forty".