21206124356 has 12 divisors (see below), whose sum is σ = 37303002492. Its totient is φ = 10548123648.

The previous prime is 21206124353. The next prime is 21206124397. The reversal of 21206124356 is 65342160212.

It can be written as a sum of positive squares in 2 ways, for example, as 6520562500 + 14685561856 = 80750^2 + 121184^2 .

It is not an unprimeable number, because it can be changed into a prime (21206124353) 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, 13733765 + ... + 13735308.

It is an arithmetic number, because the mean of its divisors is an integer number (3108583541).

Almost surely, 2^21206124356 is an apocalyptic number.

It is an amenable number.

21206124356 is a deficient number, since it is larger than the sum of its proper divisors (16096878136).

21206124356 is a wasteful number, since it uses less digits than its factorization.

21206124356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27469270 (or 27469268 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 32.

Adding to 21206124356 its reverse (65342160212), we get a palindrome (86548284568).

The spelling of 21206124356 in words is "twenty-one billion, two hundred six million, one hundred twenty-four thousand, three hundred fifty-six".