21155165221025 has 24 divisors (see below), whose sum is σ = 30123335748000. Its totient is φ = 14575807612800.

The previous prime is 21155165221009. The next prime is 21155165221039. The reversal of 21155165221025 is 52012256155112.

It is not a de Polignac number, because 21155165221025 - 2⁴ = 21155165221009 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21155165221025.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2024412500 + ... + 2024422949.

It is an arithmetic number, because the mean of its divisors is an integer number (1255138989500).

Almost surely, 2^{21155165221025} is an apocalyptic number.

21155165221025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21155165221025 is a deficient number, since it is larger than the sum of its proper divisors (8968170526975).

21155165221025 is a wasteful number, since it uses less digits than its factorization.

21155165221025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4048835489 (or 4048835484 counting only the distinct ones).

The product of its (nonzero) digits is 60000, while the sum is 38.

The spelling of 21155165221025 in words is "twenty-one trillion, one hundred fifty-five billion, one hundred sixty-five million, two hundred twenty-one thousand, twenty-five".