81621719794 has 8 divisors (see below), whose sum is σ = 122571552348. Its totient is φ = 40764535680.

The previous prime is 81621719783. The next prime is 81621719801. The reversal of 81621719794 is 49791712618.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 72018699769 + 9603020025 = 268363^2 + 97995^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23159907 + ... + 23163430.

Almost surely, 2^81621719794 is an apocalyptic number.

81621719794 is a deficient number, since it is larger than the sum of its proper divisors (40949832554).

81621719794 is a wasteful number, since it uses less digits than its factorization.

81621719794 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46324220.

The product of its digits is 1524096, while the sum is 55.

The spelling of 81621719794 in words is "eighty-one billion, six hundred twenty-one million, seven hundred nineteen thousand, seven hundred ninety-four".