21020019999991 has 2 divisors, whose sum is σ = 21020019999992. Its totient is φ = 21020019999990.

The previous prime is 21020019999973. The next prime is 21020020000043. The reversal of 21020019999991 is 19999991002012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21020019999991 - 2³¹ = 21017872516343 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020019999191) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510009999995 + 10510009999996.

It is an arithmetic number, because the mean of its divisors is an integer number (10510009999996).

Almost surely, 2^{21020019999991} is an apocalyptic number.

21020019999991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020019999991 is an equidigital number, since it uses as much as digits as its factorization.

21020019999991 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2125764, while the sum is 61.

The spelling of 21020019999991 in words is "twenty-one trillion, twenty billion, nineteen million, nine hundred ninety-nine thousand, nine hundred ninety-one".