21155002145 has 4 divisors (see below), whose sum is σ = 25386002580. Its totient is φ = 16924001712.

The previous prime is 21155002139. The next prime is 21155002159. The reversal of 21155002145 is 54120055112.

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 8614809856 + 12540192289 = 92816^2 + 111983^2 .

It is a cyclic number.

It is not a de Polignac number, because 21155002145 - 2¹⁶ = 21154936609 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, 2115500210 + ... + 2115500219.

It is an arithmetic number, because the mean of its divisors is an integer number (6346500645).

Almost surely, 2^21155002145 is an apocalyptic number.

It is an amenable number.

21155002145 is a deficient number, since it is larger than the sum of its proper divisors (4231000435).

21155002145 is an equidigital number, since it uses as much as digits as its factorization.

21155002145 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4231000434.

The product of its (nonzero) digits is 2000, while the sum is 26.

Adding to 21155002145 its reverse (54120055112), we get a palindrome (75275057257).

The spelling of 21155002145 in words is "twenty-one billion, one hundred fifty-five million, two thousand, one hundred forty-five".