20121545221 has 4 divisors (see below), whose sum is σ = 20172229612. Its totient is φ = 20070860832.

The previous prime is 20121545209. The next prime is 20121545233. The reversal of 20121545221 is 12254512102.

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 (20121545209) and next prime (20121545233).

It can be written as a sum of positive squares in 2 ways, for example, as 13124222721 + 6997322500 = 114561^2 + 83650^2 .

It is a cyclic number.

It is not a de Polignac number, because 20121545221 - 2²⁹ = 19584674309 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20121545261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 25341600 + ... + 25342393.

It is an arithmetic number, because the mean of its divisors is an integer number (5043057403).

Almost surely, 2^20121545221 is an apocalyptic number.

It is an amenable number.

20121545221 is a deficient number, since it is larger than the sum of its proper divisors (50684391).

20121545221 is an equidigital number, since it uses as much as digits as its factorization.

20121545221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50684390.

The product of its (nonzero) digits is 1600, while the sum is 25.

The spelling of 20121545221 in words is "twenty billion, one hundred twenty-one million, five hundred forty-five thousand, two hundred twenty-one".