81212721293 has 8 divisors (see below), whose sum is σ = 91453622016. Its totient is φ = 71448141600.

The previous prime is 81212721257. The next prime is 81212721299. The reversal of 81212721293 is 39212721218.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81212721293 - 2¹² = 81212717197 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81212721299) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 119079896 + ... + 119080577.

It is an arithmetic number, because the mean of its divisors is an integer number (11431702752).

Almost surely, 2^81212721293 is an apocalyptic number.

It is an amenable number.

81212721293 is a deficient number, since it is larger than the sum of its proper divisors (10240900723).

81212721293 is a wasteful number, since it uses less digits than its factorization.

81212721293 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 238160515.

The product of its digits is 24192, while the sum is 38.

The spelling of 81212721293 in words is "eighty-one billion, two hundred twelve million, seven hundred twenty-one thousand, two hundred ninety-three".