21155532121563 has 32 divisors (see below), whose sum is σ = 32503578401280. Its totient is φ = 11989094757120.

The previous prime is 21155532121547. The next prime is 21155532121673. The reversal of 21155532121563 is 36512123555112.

It is not a de Polignac number, because 21155532121563 - 2⁴ = 21155532121547 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21155532121363) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1132308 + ... + 6602513.

It is an arithmetic number, because the mean of its divisors is an integer number (1015736825040).

Almost surely, 2^{21155532121563} is an apocalyptic number.

21155532121563 is a deficient number, since it is larger than the sum of its proper divisors (11348046279717).

21155532121563 is a wasteful number, since it uses less digits than its factorization.

21155532121563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7735907.

The product of its digits is 270000, while the sum is 42.

Adding to 21155532121563 its reverse (36512123555112), we get a palindrome (57667655676675).

The spelling of 21155532121563 in words is "twenty-one trillion, one hundred fifty-five billion, five hundred thirty-two million, one hundred twenty-one thousand, five hundred sixty-three".