21165155215 has 4 divisors (see below), whose sum is σ = 25398186264. Its totient is φ = 16932124168.

The previous prime is 21165155191. The next prime is 21165155239. The reversal of 21165155215 is 51255156112.

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

It is an interprime number because it is at equal distance from previous prime (21165155191) and next prime (21165155239).

It is a cyclic number.

It is not a de Polignac number, because 21165155215 - 2¹³ = 21165147023 is a prime.

It is a Duffinian number.

It is a congruent 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, 2116515517 + ... + 2116515526.

It is an arithmetic number, because the mean of its divisors is an integer number (6349546566).

Almost surely, 2^21165155215 is an apocalyptic number.

21165155215 is a deficient number, since it is larger than the sum of its proper divisors (4233031049).

21165155215 is an equidigital number, since it uses as much as digits as its factorization.

21165155215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4233031048.

The product of its digits is 15000, while the sum is 34.

The spelling of 21165155215 in words is "twenty-one billion, one hundred sixty-five million, one hundred fifty-five thousand, two hundred fifteen".