21251420091 has 30 divisors (see below), whose sum is σ = 34894323156. Its totient is φ = 12879642600.

The previous prime is 21251420059. The next prime is 21251420107. The reversal of 21251420091 is 19002415212.

It is not a de Polignac number, because 21251420091 - 2⁵ = 21251420059 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21251420051) by changing a digit.

It is a polite number, since it can be written in 29 ways as a sum of consecutive naturals, for example, 1074345 + ... + 1093946.

Almost surely, 2^21251420091 is an apocalyptic number.

21251420091 is a deficient number, since it is larger than the sum of its proper divisors (13642903065).

21251420091 is a wasteful number, since it uses less digits than its factorization.

21251420091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2168325 (or 2168305 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 27.

The spelling of 21251420091 in words is "twenty-one billion, two hundred fifty-one million, four hundred twenty thousand, ninety-one".