20211021109978 has 4 divisors (see below), whose sum is σ = 30316531664970. Its totient is φ = 10105510554988.

The previous prime is 20211021109973. The next prime is 20211021110011. The reversal of 20211021109978 is 87990112011202.

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 only one way, i.e., 13652899370289 + 6558121739689 = 3694983^2 + 2560883^2 .

It is not an unprimeable number, because it can be changed into a prime (20211021109973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5052755277493 + ... + 5052755277496.

Almost surely, 2^{20211021109978} is an apocalyptic number.

20211021109978 is a deficient number, since it is larger than the sum of its proper divisors (10105510554992).

20211021109978 is a wasteful number, since it uses less digits than its factorization.

20211021109978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10105510554991.

The product of its (nonzero) digits is 36288, while the sum is 43.

The spelling of 20211021109978 in words is "twenty trillion, two hundred eleven billion, twenty-one million, one hundred nine thousand, nine hundred seventy-eight".