19999999 has 2 divisors, whose sum is σ = 20000000.
Its totient is φ = 19999998.
The previous prime is 19999981. The next prime is 20000003. The reversal of 19999999 is 99999991.
It can be divided in two parts, 19 and 999999, that multiplied together give a palindrome (18999981).
It is a strong prime.
It is a cyclic number.
It is not a de Polignac number, because 19999999 - 221 = 17902847 is a prime.
It is a fibodiv number, since the Fibonacci-like sequence with seeds 1 and 9999999 contains 19999999 itself.
19999999 is a modest number, since divided by 9999 gives 1999 as remainder.
It is a plaindrome in base 10.
It is a self number, because there is not a number n which added to its sum of digits gives 19999999.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (19999909) by changing a digit.
It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9999999 + 10000000.
It is an arithmetic number, because the mean of its divisors is an integer number (10000000).
Almost surely, 219999999 is an apocalyptic number.
19999999 is a deficient number, since it is larger than the sum of its proper divisors (1).
19999999 is an equidigital number, since it uses as much as digits as its factorization.
19999999 is an odious number, because the sum of its binary digits is odd.
The product of its digits is 4782969, while the sum is 64.
The square root of 19999999 is about 4472.1358431962.
The cubic root of 19999999 is about 271.4417571355.
The spelling of 19999999 in words is "nineteen million, nine hundred ninety-nine thousand, nine hundred ninety-nine".