1999978 has 8 divisors (see below), whose sum is σ = 3157920.
Its totient is φ = 947340.
The previous prime is 1999969. The next prime is 1999979. The reversal of 1999978 is 8799991.
It is a sphenic number, since it is the product of 3 distinct primes.
It is not an unprimeable number, because it can be changed into a prime (1999979) 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, 26278 + ... + 26353.
It is an arithmetic number, because the mean of its divisors is an integer number (394740).
21999978 is an apocalyptic number.
1999978 is a deficient number, since it is larger than the sum of its proper divisors (1157942).
1999978 is a wasteful number, since it uses less digits than its factorization.
1999978 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 52652.
The product of its digits is 367416, while the sum is 52.
The square root of 1999978 is about 1414.2057841771.
The cubic root of 1999978 is about 125.9916430167.
The spelling of 1999978 in words is "one million, nine hundred ninety-nine thousand, nine hundred seventy-eight".