81780000 has 240 divisors, whose sum is σ = 283409280. Its totient is φ = 20608000.

The previous prime is 81779989. The next prime is 81780011. The reversal of 81780000 is 8718.

It is an interprime number because it is at equal distance from previous prime (81779989) and next prime (81780011).

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1739977 + ... + 1740023.

It is an arithmetic number, because the mean of its divisors is an integer number (1180872).

Almost surely, 2^81780000 is an apocalyptic number.

81780000 is a gapful number since it is divisible by the number (80) 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 81780000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (141704640).

81780000 is an abundant number, since it is smaller than the sum of its proper divisors (201629280).

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

81780000 is a wasteful number, since it uses less digits than its factorization.

81780000 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109 (or 86 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 24.

The square root of 81780000 is about 9043.2295116291. The cubic root of 81780000 is about 434.0592697268.

Adding to 81780000 its reverse (8718), we get a palindrome (81788718).

The spelling of 81780000 in words is "eighty-one million, seven hundred eighty thousand".