21020838978 has 16 divisors (see below), whose sum is σ = 42514057440. Its totient is φ = 6928216416.

The previous prime is 21020838977. The next prime is 21020838991. The reversal of 21020838978 is 87983802012.

It is not an unprimeable number, because it can be changed into a prime (21020838977) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19681900 + ... + 19682967.

It is an arithmetic number, because the mean of its divisors is an integer number (2657128590).

Almost surely, 2^21020838978 is an apocalyptic number.

21020838978 is an abundant number, since it is smaller than the sum of its proper divisors (21493218462).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21020838978 is a wasteful number, since it uses less digits than its factorization.

21020838978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39364961.

The product of its (nonzero) digits is 387072, while the sum is 48.

The spelling of 21020838978 in words is "twenty-one billion, twenty million, eight hundred thirty-eight thousand, nine hundred seventy-eight".