81026849978 has 4 divisors (see below), whose sum is σ = 121540274970. Its totient is φ = 40513424988.

The previous prime is 81026849963. The next prime is 81026849999. The reversal of 81026849978 is 87994862018.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 80334265489 + 692584489 = 283433^2 + 26317^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 81026849978.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20256712493 + ... + 20256712496.

Almost surely, 2^81026849978 is an apocalyptic number.

81026849978 is a deficient number, since it is larger than the sum of its proper divisors (40513424992).

81026849978 is a wasteful number, since it uses less digits than its factorization.

81026849978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40513424991.

The product of its (nonzero) digits is 13934592, while the sum is 62.

The spelling of 81026849978 in words is "eighty-one billion, twenty-six million, eight hundred forty-nine thousand, nine hundred seventy-eight".