21508265755 has 16 divisors (see below), whose sum is σ = 26529651360. Its totient is φ = 16732538368.

The previous prime is 21508265741. The next prime is 21508265759. The reversal of 21508265755 is 55756280512.

It is a cyclic number.

It is not a de Polignac number, because 21508265755 - 2¹⁵ = 21508232987 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21508265759) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 329185 + ... + 389074.

It is an arithmetic number, because the mean of its divisors is an integer number (1658103210).

Almost surely, 2^21508265755 is an apocalyptic number.

21508265755 is a deficient number, since it is larger than the sum of its proper divisors (5021385605).

21508265755 is a wasteful number, since it uses less digits than its factorization.

21508265755 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 718430.

The product of its (nonzero) digits is 840000, while the sum is 46.

The spelling of 21508265755 in words is "twenty-one billion, five hundred eight million, two hundred sixty-five thousand, seven hundred fifty-five".