21267720 has 48 divisors (see below), whose sum is σ = 69121260. Its totient is φ = 5671296.

The previous prime is 21267713. The next prime is 21267721. The reversal of 21267720 is 2776212.

It can be written as a sum of positive squares in 2 ways, for example, as 20088324 + 1179396 = 4482^2 + 1086^2 .

It is not an unprimeable number, because it can be changed into a prime (21267721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 29179 + ... + 29898.

Almost surely, 2^21267720 is an apocalyptic number.

21267720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21267720 is an abundant number, since it is smaller than the sum of its proper divisors (47853540).

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

21267720 is a wasteful number, since it uses less digits than its factorization.

21267720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 59094 (or 59087 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 21267720 is about 4611.6938319884. The cubic root of 21267720 is about 277.0598818350.

The spelling of 21267720 in words is "twenty-one million, two hundred sixty-seven thousand, seven hundred twenty".