18721834 has 4 divisors (see below), whose sum is σ = 28082754. Its totient is φ = 9360916.

The previous prime is 18721823. The next prime is 18721837. The reversal of 18721834 is 43812781.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 43812781 = 2381 ⋅18401.

It can be written as a sum of positive squares in only one way, i.e., 10909809 + 7812025 = 3303^2 + 2795^2 .

It is an alternating number because its digits alternate between odd and even.

It is a self number, because there is not a number n which added to its sum of digits gives 18721834.

It is not an unprimeable number, because it can be changed into a prime (18721837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4680457 + ... + 4680460.

Almost surely, 2^18721834 is an apocalyptic number.

18721834 is a deficient number, since it is larger than the sum of its proper divisors (9360920).

18721834 is an equidigital number, since it uses as much as digits as its factorization.

18721834 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9360919.

The product of its digits is 10752, while the sum is 34.

The square root of 18721834 is about 4326.8734670660. The cubic root of 18721834 is about 265.5315496689.

The spelling of 18721834 in words is "eighteen million, seven hundred twenty-one thousand, eight hundred thirty-four".