19999990 has 32 divisors (see below), whose sum is σ = 38677824. Its totient is φ = 7418880.

The previous prime is 19999981. The next prime is 19999999. The reversal of 19999990 is 9999991.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (19999981) and next prime (19999999).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19999999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11242 + ... + 12898.

It is an arithmetic number, because the mean of its divisors is an integer number (1208682).

Almost surely, 2^19999990 is an apocalyptic number.

19999990 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

19999990 is a deficient number, since it is larger than the sum of its proper divisors (18677834).

19999990 is a wasteful number, since it uses less digits than its factorization.

19999990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1752.

The product of its (nonzero) digits is 531441, while the sum is 55.

The square root of 19999990 is about 4472.1348369655. The cubic root of 19999990 is about 271.4417164192.

Subtracting from 19999990 its reverse (9999991), we obtain a palindrome (9999999).

The spelling of 19999990 in words is "nineteen million, nine hundred ninety-nine thousand, nine hundred ninety".