21531240212 has 6 divisors (see below), whose sum is σ = 37679670378. Its totient is φ = 10765620104.

The previous prime is 21531240187. The next prime is 21531240221. The reversal of 21531240212 is 21204213512.

It can be written as a sum of positive squares in only one way, i.e., 12643653136 + 8887587076 = 112444^2 + 94274^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2691405023 + ... + 2691405030.

It is an arithmetic number, because the mean of its divisors is an integer number (6279945063).

Almost surely, 2^21531240212 is an apocalyptic number.

It is an amenable number.

21531240212 is a deficient number, since it is larger than the sum of its proper divisors (16148430166).

21531240212 is a wasteful number, since it uses less digits than its factorization.

21531240212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5382810057 (or 5382810055 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 23.

Adding to 21531240212 its reverse (21204213512), we get a palindrome (42735453724).

The spelling of 21531240212 in words is "twenty-one billion, five hundred thirty-one million, two hundred forty thousand, two hundred twelve".