21212010091 has 4 divisors (see below), whose sum is σ = 21213752112. Its totient is φ = 21210268072.

The previous prime is 21212010047. The next prime is 21212010097. The reversal of 21212010091 is 19001021212.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21212010091 - 2²¹ = 21209912939 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212010097) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 852616 + ... + 877141.

It is an arithmetic number, because the mean of its divisors is an integer number (5303438028).

Almost surely, 2^21212010091 is an apocalyptic number.

21212010091 is a deficient number, since it is larger than the sum of its proper divisors (1742021).

21212010091 is a wasteful number, since it uses less digits than its factorization.

21212010091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1742020.

The product of its (nonzero) digits is 72, while the sum is 19.

The spelling of 21212010091 in words is "twenty-one billion, two hundred twelve million, ten thousand, ninety-one".