19971812 has 72 divisors (see below), whose sum is σ = 44432640. Its totient is φ = 7801920.

The previous prime is 19971761. The next prime is 19971857. The reversal of 19971812 is 21817991.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 115358 + ... + 115530.

It is an arithmetic number, because the mean of its divisors is an integer number (617120).

Almost surely, 2^19971812 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19971812, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22216320).

19971812 is an abundant number, since it is smaller than the sum of its proper divisors (24460828).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

19971812 is a wasteful number, since it uses less digits than its factorization.

19971812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 241 (or 232 counting only the distinct ones).

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

The square root of 19971812 is about 4468.9833295728. The cubic root of 19971812 is about 271.3141783624.

The spelling of 19971812 in words is "nineteen million, nine hundred seventy-one thousand, eight hundred twelve".