19971518 has 20 divisors (see below), whose sum is σ = 34956480. Its totient is φ = 8557164.

The previous prime is 19971509. The next prime is 19971541. The reversal of 19971518 is 81517991.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 2723 + ... + 6881.

It is an arithmetic number, because the mean of its divisors is an integer number (1747824).

Almost surely, 2^19971518 is an apocalyptic number.

19971518 is a deficient number, since it is larger than the sum of its proper divisors (14984962).

19971518 is an frugal number, since it uses more digits than its factorization.

19971518 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4189 (or 4168 counting only the distinct ones).

The product of its digits is 22680, while the sum is 41.

The square root of 19971518 is about 4468.9504360644. The cubic root of 19971518 is about 271.3128470401.

It can be divided in two parts, 199 and 71518, that added together give a palindrome (71717).

The spelling of 19971518 in words is "nineteen million, nine hundred seventy-one thousand, five hundred eighteen".