20511671221621 has 4 divisors (see below), whose sum is σ = 20511883327500. Its totient is φ = 20511459115744.

The previous prime is 20511671221619. The next prime is 20511671221669. The reversal of 20511671221621 is 12612217611502.

It is a happy number.

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 19581775516900 + 929895704721 = 4425130^2 + 964311^2 .

It is a cyclic number.

It is not a de Polignac number, because 20511671221621 - 2¹ = 20511671221619 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 (20511671221021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 105907816 + ... + 106101313.

It is an arithmetic number, because the mean of its divisors is an integer number (5127970831875).

Almost surely, 2^{20511671221621} is an apocalyptic number.

It is an amenable number.

20511671221621 is a deficient number, since it is larger than the sum of its proper divisors (212105879).

20511671221621 is an equidigital number, since it uses as much as digits as its factorization.

20511671221621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212105878.

The product of its (nonzero) digits is 20160, while the sum is 37.

The spelling of 20511671221621 in words is "twenty trillion, five hundred eleven billion, six hundred seventy-one million, two hundred twenty-one thousand, six hundred twenty-one".