21020045155 has 4 divisors (see below), whose sum is σ = 25224054192. Its totient is φ = 16816036120.

The previous prime is 21020045041. The next prime is 21020045183. The reversal of 21020045155 is 55154002012.

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

It is not a de Polignac number, because 21020045155 - 2⁷ = 21020045027 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, 2102004511 + ... + 2102004520.

It is an arithmetic number, because the mean of its divisors is an integer number (6306013548).

Almost surely, 2^21020045155 is an apocalyptic number.

21020045155 is a deficient number, since it is larger than the sum of its proper divisors (4204009037).

21020045155 is an equidigital number, since it uses as much as digits as its factorization.

21020045155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4204009036.

The product of its (nonzero) digits is 2000, while the sum is 25.

Adding to 21020045155 its reverse (55154002012), we get a palindrome (76174047167).

The spelling of 21020045155 in words is "twenty-one billion, twenty million, forty-five thousand, one hundred fifty-five".