81914750521 has 4 divisors (see below), whose sum is σ = 86226053200. Its totient is φ = 77603447844.

The previous prime is 81914750513. The next prime is 81914750531. The reversal of 81914750521 is 12505741918.

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 an emirpimes, since its reverse is a distinct semiprime: 12505741918 = 2 ⋅6252870959.

It is a cyclic number.

It is not a de Polignac number, because 81914750521 - 2³ = 81914750513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81914750531) 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, 2155651311 + ... + 2155651348.

It is an arithmetic number, because the mean of its divisors is an integer number (21556513300).

Almost surely, 2^81914750521 is an apocalyptic number.

It is an amenable number.

81914750521 is a deficient number, since it is larger than the sum of its proper divisors (4311302679).

81914750521 is a wasteful number, since it uses less digits than its factorization.

81914750521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4311302678.

The product of its (nonzero) digits is 100800, while the sum is 43.

The spelling of 81914750521 in words is "eighty-one billion, nine hundred fourteen million, seven hundred fifty thousand, five hundred twenty-one".