91819191820 has 24 divisors (see below), whose sum is σ = 192938883984. Its totient is φ = 36705089856.

The previous prime is 91819191811. The next prime is 91819191847. The reversal of 91819191820 is 2819191819.

It is a happy number.

It is a hoax number, since the sum of its digits (49) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1378327 + ... + 1443406.

It is an arithmetic number, because the mean of its divisors is an integer number (8039120166).

Almost surely, 2^91819191820 is an apocalyptic number.

It is an amenable number.

91819191820 is an abundant number, since it is smaller than the sum of its proper divisors (101119692164).

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

91819191820 is a wasteful number, since it uses less digits than its factorization.

91819191820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2823369 (or 2823367 counting only the distinct ones).

The product of its (nonzero) digits is 93312, while the sum is 49.

The spelling of 91819191820 in words is "ninety-one billion, eight hundred nineteen million, one hundred ninety-one thousand, eight hundred twenty".