1911999978 has 40 divisors (see below), whose sum is σ = 4896341472. Its totient is φ = 546285384.

The previous prime is 1911999953. The next prime is 1912000003. The reversal of 1911999978 is 8799991191.

It is an interprime number because it is at equal distance from previous prime (1911999953) and next prime (1912000003).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 841900 + ... + 844167.

Almost surely, 2^1911999978 is an apocalyptic number.

1911999978 is a gapful number since it is divisible by the number (18) formed by its first and last digit.

1911999978 is an abundant number, since it is smaller than the sum of its proper divisors (2984341494).

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

1911999978 is a wasteful number, since it uses less digits than its factorization.

1911999978 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1686088 (or 1686079 counting only the distinct ones).

The product of its digits is 3306744, while the sum is 63.

The square root of 1911999978 is about 43726.4219665867. The cubic root of 1911999978 is about 1241.1643542188.

The spelling of 1911999978 in words is "one billion, nine hundred eleven million, nine hundred ninety-nine thousand, nine hundred seventy-eight".