21020838977 has 2 divisors, whose sum is σ = 21020838978. Its totient is φ = 21020838976.

The previous prime is 21020838967. The next prime is 21020838991. The reversal of 21020838977 is 77983802012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18982226176 + 2038612801 = 137776^2 + 45151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020838977 - 2¹⁰ = 21020837953 is a prime.

It is not a weakly prime, because it can be changed into another prime (21020838967) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510419488 + 10510419489.

It is an arithmetic number, because the mean of its divisors is an integer number (10510419489).

Almost surely, 2^21020838977 is an apocalyptic number.

It is an amenable number.

21020838977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020838977 is an equidigital number, since it uses as much as digits as its factorization.

21020838977 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 338688, while the sum is 47.

The spelling of 21020838977 in words is "twenty-one billion, twenty million, eight hundred thirty-eight thousand, nine hundred seventy-seven".