21506129361 has 12 divisors (see below), whose sum is σ = 32891727492. Its totient is φ = 13494041856.

The previous prime is 21506129357. The next prime is 21506129389. The reversal of 21506129361 is 16392160512.

21506129361 is a `hidden beast` number, since 2 + 1 + 5 + 0 + 612 + 9 + 36 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15185879361 + 6320250000 = 123231^2 + 79500^2 .

It is not a de Polignac number, because 21506129361 - 2² = 21506129357 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21506129311) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 70281316 + ... + 70281621.

It is an arithmetic number, because the mean of its divisors is an integer number (2740977291).

Almost surely, 2^21506129361 is an apocalyptic number.

It is an amenable number.

21506129361 is a deficient number, since it is larger than the sum of its proper divisors (11385598131).

21506129361 is a wasteful number, since it uses less digits than its factorization.

21506129361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140562960 (or 140562957 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

Adding to 21506129361 its reverse (16392160512), we get a palindrome (37898289873).

The spelling of 21506129361 in words is "twenty-one billion, five hundred six million, one hundred twenty-nine thousand, three hundred sixty-one".