21981212755 has 16 divisors (see below), whose sum is σ = 27934883424. Its totient is φ = 16547115520.

The previous prime is 21981212753. The next prime is 21981212761. The reversal of 21981212755 is 55721218912.

It is not a de Polignac number, because 21981212755 - 2¹ = 21981212753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21981212753) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 429060 + ... + 477550.

It is an arithmetic number, because the mean of its divisors is an integer number (1745930214).

Almost surely, 2^21981212755 is an apocalyptic number.

21981212755 is a deficient number, since it is larger than the sum of its proper divisors (5953670669).

21981212755 is a wasteful number, since it uses less digits than its factorization.

21981212755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53846.

The product of its digits is 100800, while the sum is 43.

The spelling of 21981212755 in words is "twenty-one billion, nine hundred eighty-one million, two hundred twelve thousand, seven hundred fifty-five".