21531201361 has 2 divisors, whose sum is σ = 21531201362. Its totient is φ = 21531201360.

The previous prime is 21531201353. The next prime is 21531201383. The reversal of 21531201361 is 16310213512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21041243136 + 489958225 = 145056^2 + 22135^2 .

It is a cyclic number.

It is not a de Polignac number, because 21531201361 - 2³ = 21531201353 is a prime.

It is not a weakly prime, because it can be changed into another prime (21531207361) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765600680 + 10765600681.

It is an arithmetic number, because the mean of its divisors is an integer number (10765600681).

Almost surely, 2^21531201361 is an apocalyptic number.

It is an amenable number.

21531201361 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531201361 is an equidigital number, since it uses as much as digits as its factorization.

21531201361 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 25.

Adding to 21531201361 its reverse (16310213512), we get a palindrome (37841414873).

The spelling of 21531201361 in words is "twenty-one billion, five hundred thirty-one million, two hundred one thousand, three hundred sixty-one".