81214986721 has 4 divisors (see below), whose sum is σ = 88598167344. Its totient is φ = 73831806100.

The previous prime is 81214986719. The next prime is 81214986767. The reversal of 81214986721 is 12768941218.

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.

It is a cyclic number.

It is not a de Polignac number, because 81214986721 - 2¹ = 81214986719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81214986521) 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, 3691590295 + ... + 3691590316.

It is an arithmetic number, because the mean of its divisors is an integer number (22149541836).

Almost surely, 2^81214986721 is an apocalyptic number.

It is an amenable number.

81214986721 is a deficient number, since it is larger than the sum of its proper divisors (7383180623).

81214986721 is a wasteful number, since it uses less digits than its factorization.

81214986721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7383180622.

The product of its digits is 387072, while the sum is 49.

The spelling of 81214986721 in words is "eighty-one billion, two hundred fourteen million, nine hundred eighty-six thousand, seven hundred twenty-one".