21020012091 has 24 divisors (see below), whose sum is σ = 32730007856. Its totient is φ = 12922649280.

The previous prime is 21020012081. The next prime is 21020012099. The reversal of 21020012091 is 19021002012.

It is not a de Polignac number, because 21020012091 - 2⁵ = 21020012059 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21020012099) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 31476 + ... + 207438.

Almost surely, 2^21020012091 is an apocalyptic number.

21020012091 is a deficient number, since it is larger than the sum of its proper divisors (11709995765).

21020012091 is a wasteful number, since it uses less digits than its factorization.

21020012091 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 177003 (or 177000 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 18.

It can be divided in two parts, 210 and 20012091, that added together give a triangular number (20012301 = T₆₃₂₆).

The spelling of 21020012091 in words is "twenty-one billion, twenty million, twelve thousand, ninety-one".