21151115065 has 4 divisors (see below), whose sum is σ = 25381338084. Its totient is φ = 16920892048.

The previous prime is 21151115057. The next prime is 21151115087. The reversal of 21151115065 is 56051115112.

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 14193386496 + 6957728569 = 119136^2 + 83413^2 .

It is a cyclic number.

It is not a de Polignac number, because 21151115065 - 2³ = 21151115057 is a prime.

It is a Duffinian number.

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 3 ways as a sum of consecutive naturals, for example, 2115111502 + ... + 2115111511.

It is an arithmetic number, because the mean of its divisors is an integer number (6345334521).

Almost surely, 2^21151115065 is an apocalyptic number.

It is an amenable number.

21151115065 is a deficient number, since it is larger than the sum of its proper divisors (4230223019).

21151115065 is an equidigital number, since it uses as much as digits as its factorization.

21151115065 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4230223018.

The product of its (nonzero) digits is 1500, while the sum is 28.

It can be divided in two parts, 211511 and 15065, that added together give a square (226576 = 476²).

The spelling of 21151115065 in words is "twenty-one billion, one hundred fifty-one million, one hundred fifteen thousand, sixty-five".