19910990 has 32 divisors (see below), whose sum is σ = 40366080. Its totient is φ = 7005600.

The previous prime is 19910983. The next prime is 19910999. The reversal of 19910990 is 9901991.

It is a happy number.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax 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 (19910999) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 491 + ... + 6329.

It is an arithmetic number, because the mean of its divisors is an integer number (1261440).

Almost surely, 2^19910990 is an apocalyptic number.

19910990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

19910990 is an abundant number, since it is smaller than the sum of its proper divisors (20455090).

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

19910990 is a wasteful number, since it uses less digits than its factorization.

19910990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5888.

The product of its (nonzero) digits is 6561, while the sum is 38.

The square root of 19910990 is about 4462.1732373363. The cubic root of 19910990 is about 271.0384789431.

The spelling of 19910990 in words is "nineteen million, nine hundred ten thousand, nine hundred ninety".