81516440 has 16 divisors (see below), whose sum is σ = 183412080. Its totient is φ = 32606560.

The previous prime is 81516437. The next prime is 81516451. The reversal of 81516440 is 4461518.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1018916 + ... + 1018995.

It is an arithmetic number, because the mean of its divisors is an integer number (11463255).

Almost surely, 2^81516440 is an apocalyptic number.

It is an amenable number.

81516440 is an abundant number, since it is smaller than the sum of its proper divisors (101895640).

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

81516440 is a wasteful number, since it uses less digits than its factorization.

81516440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2037922 (or 2037918 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 81516440 is about 9028.6455241083. The cubic root of 81516440 is about 433.5924735330.

Adding to 81516440 its reverse (4461518), we get a palindrome (85977958).

The spelling of 81516440 in words is "eighty-one million, five hundred sixteen thousand, four hundred forty".