81216697851 has 24 divisors (see below), whose sum is σ = 118129752000. Its totient is φ = 53768336112.

The previous prime is 81216697847. The next prime is 81216697873. The reversal of 81216697851 is 15879661218.

It is a happy number.

It is not a de Polignac number, because 81216697851 - 2² = 81216697847 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81216697811) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1156420 + ... + 1224638.

It is an arithmetic number, because the mean of its divisors is an integer number (4922073000).

Almost surely, 2^81216697851 is an apocalyptic number.

81216697851 is a deficient number, since it is larger than the sum of its proper divisors (36913054149).

81216697851 is a wasteful number, since it uses less digits than its factorization.

81216697851 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69143 (or 69140 counting only the distinct ones).

The product of its digits is 1451520, while the sum is 54.

The spelling of 81216697851 in words is "eighty-one billion, two hundred sixteen million, six hundred ninety-seven thousand, eight hundred fifty-one".