81216840 has 32 divisors (see below), whose sum is σ = 243650880. Its totient is φ = 21657792.

The previous prime is 81216833. The next prime is 81216847. The reversal of 81216840 is 4861218.

It is an interprime number because it is at equal distance from previous prime (81216833) and next prime (81216847).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 81216798 and 81216807.

It is not an unprimeable number, because it can be changed into a prime (81216847) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 338284 + ... + 338523.

It is an arithmetic number, because the mean of its divisors is an integer number (7614090).

Almost surely, 2^81216840 is an apocalyptic number.

It is an amenable number.

81216840 is an abundant number, since it is smaller than the sum of its proper divisors (162434040).

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

81216840 is a wasteful number, since it uses less digits than its factorization.

81216840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 676821 (or 676817 counting only the distinct ones).

The product of its (nonzero) digits is 3072, while the sum is 30.

The square root of 81216840 is about 9012.0386150970. The cubic root of 81216840 is about 433.0606226246.

The spelling of 81216840 in words is "eighty-one million, two hundred sixteen thousand, eight hundred forty".