21801021167 has 4 divisors (see below), whose sum is σ = 21855935976. Its totient is φ = 21746106360.

The previous prime is 21801021163. The next prime is 21801021191. The reversal of 21801021167 is 76112010812.

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 21801021167 - 2² = 21801021163 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21801021161) 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, 27456809 + ... + 27457602.

It is an arithmetic number, because the mean of its divisors is an integer number (5463983994).

Almost surely, 2^21801021167 is an apocalyptic number.

21801021167 is a deficient number, since it is larger than the sum of its proper divisors (54914809).

21801021167 is an equidigital number, since it uses as much as digits as its factorization.

21801021167 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54914808.

The product of its (nonzero) digits is 1344, while the sum is 29.

Adding to 21801021167 its reverse (76112010812), we get a palindrome (97913031979).

The spelling of 21801021167 in words is "twenty-one billion, eight hundred one million, twenty-one thousand, one hundred sixty-seven".