18101721 has 24 divisors (see below), whose sum is σ = 27119232. Its totient is φ = 10727200.

The previous prime is 18101717. The next prime is 18101723. The reversal of 18101721 is 12710181.

It is not a de Polignac number, because 18101721 - 2² = 18101717 is a prime.

It is not an unprimeable number, because it can be changed into a prime (18101723) 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, 16531 + ... + 17591.

It is an arithmetic number, because the mean of its divisors is an integer number (1129968).

Almost surely, 2^18101721 is an apocalyptic number.

18101721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

18101721 is a deficient number, since it is larger than the sum of its proper divisors (9017511).

18101721 is a wasteful number, since it uses less digits than its factorization.

18101721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1133 (or 1122 counting only the distinct ones).

The product of its (nonzero) digits is 112, while the sum is 21.

The square root of 18101721 is about 4254.6117331667. The cubic root of 18101721 is about 262.5668872635.

The spelling of 18101721 in words is "eighteen million, one hundred one thousand, seven hundred twenty-one".