21210713 has 6 divisors (see below), whose sum is σ = 22478526. Its totient is φ = 19945152.

The previous prime is 21210703. The next prime is 21210719. The reversal of 21210713 is 31701212.

It can be written as a sum of positive squares in 3 ways, for example, as 23104 + 21187609 = 152^2 + 4603^2 .

It is not a de Polignac number, because 21210713 - 2⁴ = 21210697 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210691 and 21210700.

It is not an unprimeable number, because it can be changed into a prime (21210719) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 18431 + ... + 19547.

It is an arithmetic number, because the mean of its divisors is an integer number (3746421).

Almost surely, 2^21210713 is an apocalyptic number.

It is an amenable number.

21210713 is a deficient number, since it is larger than the sum of its proper divisors (1267813).

21210713 is an frugal number, since it uses more digits than its factorization.

21210713 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2251 (or 1134 counting only the distinct ones).

The product of its (nonzero) digits is 84, while the sum is 17.

The square root of 21210713 is about 4605.5089838149. The cubic root of 21210713 is about 276.8121121993.

Multiplying 21210713 by its sum of digits (17), we get a square (360582121 = 18989²).

21210713 divided by its sum of digits (17) gives a square (1247689 = 1117²).

Adding to 21210713 its reverse (31701212), we get a palindrome (52911925).

The spelling of 21210713 in words is "twenty-one million, two hundred ten thousand, seven hundred thirteen".