1991816278200 has 216 divisors, whose sum is σ = 7781294855880. Its totient is φ = 455272272000.

The previous prime is 1991816278147. The next prime is 1991816278201. The reversal of 1991816278200 is 28726181991.

It is a happy number.

1991816278200 is a `hidden beast` number, since 1 + 9 + 9 + 1 + 8 + 1 + 627 + 8 + 2 + 0 + 0 = 666.

It is a super-2 number, since 2×1991816278200² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991816278201) by changing a digit.

It is a polite number, since it can be written in 53 ways as a sum of consecutive naturals, for example, 11203276 + ... + 11379675.

Almost surely, 2^{1991816278200} is an apocalyptic number.

1991816278200 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1991816278200 is an abundant number, since it is smaller than the sum of its proper divisors (5789478577680).

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

1991816278200 is a wasteful number, since it uses less digits than its factorization.

1991816278200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22582987 (or 22582968 counting only the distinct ones).

The product of its (nonzero) digits is 870912, while the sum is 54.

The spelling of 1991816278200 in words is "one trillion, nine hundred ninety-one billion, eight hundred sixteen million, two hundred seventy-eight thousand, two hundred".