81451903993 has 4 divisors (see below), whose sum is σ = 81452549968. Its totient is φ = 81451258020.

The previous prime is 81451903867. The next prime is 81451903997. The reversal of 81451903993 is 39930915418.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 81451903993 - 2¹⁷ = 81451772921 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 81451903993.

It is not an unprimeable number, because it can be changed into a prime (81451903997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65343 + ... + 408868.

It is an arithmetic number, because the mean of its divisors is an integer number (20363137492).

Almost surely, 2^81451903993 is an apocalyptic number.

It is an amenable number.

81451903993 is a deficient number, since it is larger than the sum of its proper divisors (645975).

81451903993 is a wasteful number, since it uses less digits than its factorization.

81451903993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 645974.

The product of its (nonzero) digits is 1049760, while the sum is 52.

The spelling of 81451903993 in words is "eighty-one billion, four hundred fifty-one million, nine hundred three thousand, nine hundred ninety-three".