18191972 has 18 divisors (see below), whose sum is σ = 33820962. Its totient is φ = 8560384.

The previous prime is 18191939. The next prime is 18191977. The reversal of 18191972 is 27919181.

It can be written as a sum of positive squares in 3 ways, for example, as 11669056 + 6522916 = 3416^2 + 2554^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18191977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6713 + ... + 9024.

Almost surely, 2^18191972 is an apocalyptic number.

It is an amenable number.

18191972 is a deficient number, since it is larger than the sum of its proper divisors (15628990).

18191972 is a wasteful number, since it uses less digits than its factorization.

18191972 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15775 (or 15756 counting only the distinct ones).

The product of its digits is 9072, while the sum is 38.

The square root of 18191972 is about 4265.2048016479. The cubic root of 18191972 is about 263.0025300108.

The spelling of 18191972 in words is "eighteen million, one hundred ninety-one thousand, nine hundred seventy-two".