21721060 has 24 divisors (see below), whose sum is σ = 46070136. Its totient is φ = 8601600.

The previous prime is 21721057. The next prime is 21721067. The reversal of 21721060 is 6012712.

It can be written as a sum of positive squares in 4 ways, for example, as 13147876 + 8573184 = 3626^2 + 2928^2 .

It is not an unprimeable number, because it can be changed into a prime (21721067) 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, 3357 + ... + 7396.

It is an arithmetic number, because the mean of its divisors is an integer number (1919589).

Almost surely, 2^21721060 is an apocalyptic number.

21721060 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21721060 is an abundant number, since it is smaller than the sum of its proper divisors (24349076).

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

21721060 is a wasteful number, since it uses less digits than its factorization.

21721060 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10863 (or 10861 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 19.

The square root of 21721060 is about 4660.5858000899. The cubic root of 21721060 is about 279.0146487515.

Adding to 21721060 its reverse (6012712), we get a palindrome (27733772).

The spelling of 21721060 in words is "twenty-one million, seven hundred twenty-one thousand, sixty".