81081646 has 4 divisors (see below), whose sum is σ = 121622472. Its totient is φ = 40540822.

The previous prime is 81081643. The next prime is 81081661. The reversal of 81081646 is 64618018.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 64618018 = 2 ⋅32309009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81081643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20270410 + ... + 20270413.

It is an arithmetic number, because the mean of its divisors is an integer number (30405618).

Almost surely, 2^81081646 is an apocalyptic number.

81081646 is a deficient number, since it is larger than the sum of its proper divisors (40540826).

81081646 is a wasteful number, since it uses less digits than its factorization.

81081646 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40540825.

The product of its (nonzero) digits is 9216, while the sum is 34.

The square root of 81081646 is about 9004.5347464486. The cubic root of 81081646 is about 432.8201974703.

The spelling of 81081646 in words is "eighty-one million, eighty-one thousand, six hundred forty-six".