21145220505 has 20 divisors (see below), whose sum is σ = 37904766372. Its totient is φ = 11277450720.

The previous prime is 21145220491. The next prime is 21145220527. The reversal of 21145220505 is 50502254112.

21145220505 is a `hidden beast` number, since 2 + 1 + 1 + 452 + 205 + 0 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 5549207049 + 15596013456 = 74493^2 + 124884^2 .

It is not a de Polignac number, because 21145220505 - 2¹⁰ = 21145219481 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

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 19 ways as a sum of consecutive naturals, for example, 26104806 + ... + 26105615.

Almost surely, 2^21145220505 is an apocalyptic number.

It is an amenable number.

21145220505 is a deficient number, since it is larger than the sum of its proper divisors (16759545867).

21145220505 is an equidigital number, since it uses as much as digits as its factorization.

21145220505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52210438 (or 52210429 counting only the distinct ones).

The product of its (nonzero) digits is 4000, while the sum is 27.

Adding to 21145220505 its reverse (50502254112), we get a palindrome (71647474617).

The spelling of 21145220505 in words is "twenty-one billion, one hundred forty-five million, two hundred twenty thousand, five hundred five".