21561271755 has 16 divisors (see below), whose sum is σ = 34499964960. Its totient is φ = 11498701568.

The previous prime is 21561271747. The next prime is 21561271769. The reversal of 21561271755 is 55717216512.

It is a cyclic number.

It is not a de Polignac number, because 21561271755 - 2³ = 21561271747 is a prime.

It is an unprimeable number.

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, 375391 + ... + 428999.

It is an arithmetic number, because the mean of its divisors is an integer number (2156247810).

Almost surely, 2^21561271755 is an apocalyptic number.

21561271755 is a deficient number, since it is larger than the sum of its proper divisors (12938693205).

21561271755 is a wasteful number, since it uses less digits than its factorization.

21561271755 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 80430.

The product of its digits is 147000, while the sum is 42.

The spelling of 21561271755 in words is "twenty-one billion, five hundred sixty-one million, two hundred seventy-one thousand, seven hundred fifty-five".