81223641 has 20 divisors (see below), whose sum is σ = 121968000. Its totient is φ = 53866296.

The previous prime is 81223633. The next prime is 81223663. The reversal of 81223641 is 14632218.

81223641 is a `hidden beast` number, since 8 + 12 + 2 + 3 + 641 = 666.

It is not a de Polignac number, because 81223641 - 2³ = 81223633 is a prime.

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

It is not an unprimeable number, because it can be changed into a prime (81223141) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 13600 + ... + 18638.

It is an arithmetic number, because the mean of its divisors is an integer number (6098400).

Almost surely, 2^81223641 is an apocalyptic number.

81223641 is a gapful number since it is divisible by the number (81) formed by its first and last digit.

It is an amenable number.

81223641 is a deficient number, since it is larger than the sum of its proper divisors (40744359).

81223641 is a wasteful number, since it uses less digits than its factorization.

81223641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5250 (or 5241 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 81223641 is about 9012.4159358077. The cubic root of 81223641 is about 433.0727102783.

Adding to 81223641 its reverse (14632218), we get a palindrome (95855859).

The spelling of 81223641 in words is "eighty-one million, two hundred twenty-three thousand, six hundred forty-one".