21721063 has 36 divisors (see below), whose sum is σ = 28455768. Its totient is φ = 16511040.

The previous prime is 21721057. The next prime is 21721067. The reversal of 21721063 is 36012712.

It is not a de Polignac number, because 21721063 - 2⁵ = 21721031 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21721067) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 356053 + ... + 356113.

It is an arithmetic number, because the mean of its divisors is an integer number (790438).

Almost surely, 2^21721063 is an apocalyptic number.

21721063 is a deficient number, since it is larger than the sum of its proper divisors (6734705).

21721063 is a wasteful number, since it uses less digits than its factorization.

21721063 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144 (or 124 counting only the distinct ones).

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21721063 is about 4660.5861219379. The cubic root of 21721063 is about 279.0146615968.

Adding to 21721063 its reverse (36012712), we get a palindrome (57733775).

The spelling of 21721063 in words is "twenty-one million, seven hundred twenty-one thousand, sixty-three".