21006013213 has 4 divisors (see below), whose sum is σ = 21006658908. Its totient is φ = 21005367520.

The previous prime is 21006013201. The next prime is 21006013241. The reversal of 21006013213 is 31231060012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 11213327449 + 9792685764 = 105893^2 + 98958^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21006013213 is a prime.

It is a super-2 number, since 2×21006013213² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006013283) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 271306 + ... + 340027.

It is an arithmetic number, because the mean of its divisors is an integer number (5251664727).

Almost surely, 2^21006013213 is an apocalyptic number.

It is an amenable number.

21006013213 is a deficient number, since it is larger than the sum of its proper divisors (645695).

21006013213 is an equidigital number, since it uses as much as digits as its factorization.

21006013213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645694.

The product of its (nonzero) digits is 216, while the sum is 19.

Adding to 21006013213 its reverse (31231060012), we get a palindrome (52237073225).

The spelling of 21006013213 in words is "twenty-one billion, six million, thirteen thousand, two hundred thirteen".