19531981 has 8 divisors (see below), whose sum is σ = 23497280. Its totient is φ = 15860448.

The previous prime is 19531973. The next prime is 19531987. The reversal of 19531981 is 18913591.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 19531981 - 2³ = 19531973 is a prime.

It is a super-2 number, since 2×19531981² = 762996563568722, which contains 22 as substring.

It is the 4420-th Hogben number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 19531981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19531987) by changing a digit.

It is a nontrivial repunit in base 4419.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 73296 + ... + 73561.

It is an arithmetic number, because the mean of its divisors is an integer number (2937160).

Almost surely, 2^19531981 is an apocalyptic number.

It is an amenable number.

19531981 is a deficient number, since it is larger than the sum of its proper divisors (3965299).

19531981 is a wasteful number, since it uses less digits than its factorization.

19531981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 146883.

The product of its digits is 9720, while the sum is 37.

The square root of 19531981 is about 4419.5000848512. The cubic root of 19531981 is about 269.3076959812.

The spelling of 19531981 in words is "nineteen million, five hundred thirty-one thousand, nine hundred eighty-one".