91061820 has 144 divisors (see below), whose sum is σ = 294079968. Its totient is φ = 23639040.

The previous prime is 91061783. The next prime is 91061821. The reversal of 91061820 is 2816019.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (91061821) by changing a digit.

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 47 ways as a sum of consecutive naturals, for example, 199032 + ... + 199488.

It is an arithmetic number, because the mean of its divisors is an integer number (2042222).

Almost surely, 2^91061820 is an apocalyptic number.

91061820 is a gapful number since it is divisible by the number (90) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 91061820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (147039984).

91061820 is an abundant number, since it is smaller than the sum of its proper divisors (203018148).

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

91061820 is a wasteful number, since it uses less digits than its factorization.

91061820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 522 (or 508 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 91061820 is about 9542.6317124785. The cubic root of 91061820 is about 449.8959759552.

Adding to 91061820 its reverse (2816019), we get a palindrome (93877839).

The spelling of 91061820 in words is "ninety-one million, sixty-one thousand, eight hundred twenty".