81643193457 has 64 divisors (see below), whose sum is σ = 130056192000. Its totient is φ = 44571340800.

The previous prime is 81643193417. The next prime is 81643193483. The reversal of 81643193457 is 75439134618.

It is not a de Polignac number, because 81643193457 - 2⁸ = 81643193201 is a prime.

It is a super-2 number, since 2×81643193457² (a number of 23 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81643193417) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 34725832 + ... + 34728182.

It is an arithmetic number, because the mean of its divisors is an integer number (2032128000).

Almost surely, 2^81643193457 is an apocalyptic number.

81643193457 is a gapful number since it is divisible by the number (87) formed by its first and last digit.

It is an amenable number.

81643193457 is a deficient number, since it is larger than the sum of its proper divisors (48412998543).

81643193457 is a wasteful number, since it uses less digits than its factorization.

81643193457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2966.

The product of its digits is 2177280, while the sum is 51.

The spelling of 81643193457 in words is "eighty-one billion, six hundred forty-three million, one hundred ninety-three thousand, four hundred fifty-seven".