19990231 has 4 divisors (see below), whose sum is σ = 20068272. Its totient is φ = 19912192.

The previous prime is 19990213. The next prime is 19990241. The reversal of 19990231 is 13209991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 19990231 - 2⁹ = 19989719 is a prime.

It is a super-2 number, since 2×19990231² = 799218670866722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19990241) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 38635 + ... + 39148.

It is an arithmetic number, because the mean of its divisors is an integer number (5017068).

Almost surely, 2^19990231 is an apocalyptic number.

19990231 is a deficient number, since it is larger than the sum of its proper divisors (78041).

19990231 is an equidigital number, since it uses as much as digits as its factorization.

19990231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78040.

The product of its (nonzero) digits is 4374, while the sum is 34.

The square root of 19990231 is about 4471.0436141912. The cubic root of 19990231 is about 271.3975592190.

The spelling of 19990231 in words is "nineteen million, nine hundred ninety thousand, two hundred thirty-one".