21243080 has 32 divisors (see below), whose sum is σ = 49447800. Its totient is φ = 8203776.

The previous prime is 21243077. The next prime is 21243137. The reversal of 21243080 is 8034212.

It can be written as a sum of positive squares in 4 ways, for example, as 14760964 + 6482116 = 3842^2 + 2546^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7997 + ... + 10316.

Almost surely, 2^21243080 is an apocalyptic number.

21243080 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21243080 is an abundant number, since it is smaller than the sum of its proper divisors (28204720).

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

21243080 is a wasteful number, since it uses less digits than its factorization.

21243080 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18353 (or 18349 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 21243080 is about 4609.0215881464. The cubic root of 21243080 is about 276.9528433498.

Adding to 21243080 its reverse (8034212), we get a palindrome (29277292).

The spelling of 21243080 in words is "twenty-one million, two hundred forty-three thousand, eighty".