21311171545 has 4 divisors (see below), whose sum is σ = 25573405860. Its totient is φ = 17048937232.

The previous prime is 21311171509. The next prime is 21311171587. The reversal of 21311171545 is 54517111312.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9030320784 + 12280850761 = 95028^2 + 110819^2 .

It is a cyclic number.

It is not a de Polignac number, because 21311171545 - 2²⁷ = 21176953817 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2131117150 + ... + 2131117159.

It is an arithmetic number, because the mean of its divisors is an integer number (6393351465).

Almost surely, 2^21311171545 is an apocalyptic number.

It is an amenable number.

21311171545 is a deficient number, since it is larger than the sum of its proper divisors (4262234315).

21311171545 is an equidigital number, since it uses as much as digits as its factorization.

21311171545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4262234314.

The product of its digits is 4200, while the sum is 31.

Adding to 21311171545 its reverse (54517111312), we get a palindrome (75828282857).

The spelling of 21311171545 in words is "twenty-one billion, three hundred eleven million, one hundred seventy-one thousand, five hundred forty-five".