21651682091 has 4 divisors (see below), whose sum is σ = 23317196112. Its totient is φ = 19986168072.

The previous prime is 21651682079. The next prime is 21651682139. The reversal of 21651682091 is 19028615612.

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

It is a de Polignac number, because none of the positive numbers 2^k-21651682091 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21651682061) 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, 832756991 + ... + 832757016.

It is an arithmetic number, because the mean of its divisors is an integer number (5829299028).

Almost surely, 2^21651682091 is an apocalyptic number.

21651682091 is a deficient number, since it is larger than the sum of its proper divisors (1665514021).

21651682091 is a wasteful number, since it uses less digits than its factorization.

21651682091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1665514020.

The product of its (nonzero) digits is 51840, while the sum is 41.

The spelling of 21651682091 in words is "twenty-one billion, six hundred fifty-one million, six hundred eighty-two thousand, ninety-one".