20021021201978 has 4 divisors (see below), whose sum is σ = 30031531802970. Its totient is φ = 10010510600988.

The previous prime is 20021021201977. The next prime is 20021021202043. The reversal of 20021021201978 is 87910212012002.

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., 18227545813129 + 1793475388849 = 4269373^2 + 1339207^2 .

It is a super-2 number, since 2×20021021201978² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (20021021201977) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5005255300493 + ... + 5005255300496.

Almost surely, 2^{20021021201978} is an apocalyptic number.

20021021201978 is a deficient number, since it is larger than the sum of its proper divisors (10010510600992).

20021021201978 is a wasteful number, since it uses less digits than its factorization.

20021021201978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10010510600991.

The product of its (nonzero) digits is 8064, while the sum is 35.

The spelling of 20021021201978 in words is "twenty trillion, twenty-one billion, twenty-one million, two hundred one thousand, nine hundred seventy-eight".