19971813 has 8 divisors (see below), whose sum is σ = 26799328. Its totient is φ = 13229424.

The previous prime is 19971761. The next prime is 19971857. The reversal of 19971813 is 31817991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 19971813 - 2¹³ = 19963621 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19971863) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20731 + ... + 21672.

It is an arithmetic number, because the mean of its divisors is an integer number (3349916).

Almost surely, 2^19971813 is an apocalyptic number.

It is an amenable number.

19971813 is a deficient number, since it is larger than the sum of its proper divisors (6827515).

19971813 is a wasteful number, since it uses less digits than its factorization.

19971813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42563.

The product of its digits is 13608, while the sum is 39.

The square root of 19971813 is about 4468.9834414551. The cubic root of 19971813 is about 271.3141828907.

The spelling of 19971813 in words is "nineteen million, nine hundred seventy-one thousand, eight hundred thirteen".