1990 has 8 divisors (see below), whose sum is σ = 3600.
Its totient is φ = 792.
The previous prime is 1987. The next prime is 1993. The reversal of 1990 is 991.
Subtracting from 1990 its reverse (991), we obtain a palindrome (999).
It is an interprime number because it is at equal distance from previous prime (1987) and next prime (1993).
It is a sphenic number, since it is the product of 3 distinct primes.
It is a magnanimous number.
It is a plaindrome in base 12.
It is a nialpdrome in base 7, base 13 and base 14.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1993) by changing a digit.
It is a pernicious number, because its binary representation contains a prime number (7) of ones.
It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 90 + ... + 109.
It is an arithmetic number, because the mean of its divisors is an integer number (450).
21990 is an apocalyptic number.
1990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.
1990 is a deficient number, since it is larger than the sum of its proper divisors (1610).
1990 is a wasteful number, since it uses less digits than its factorization.
1990 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 206.
The product of its (nonzero) digits is 81, while the sum is 19.
The square root of 1990 is about 44.6094160464.
The cubic root of 1990 is about 12.5781767194.
The spelling of 1990 in words is "one thousand, nine hundred ninety".