81021509974802 has 4 divisors (see below), whose sum is σ = 121532264962206. Its totient is φ = 40510754987400.

The previous prime is 81021509974781. The next prime is 81021509974831. The reversal of 81021509974802 is 20847990512018.

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., 79318278778561 + 1703231196241 = 8906081^2 + 1305079^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20255377493699 + ... + 20255377493702.

Almost surely, 2^{81021509974802} is an apocalyptic number.

81021509974802 is a deficient number, since it is larger than the sum of its proper divisors (40510754987404).

81021509974802 is a wasteful number, since it uses less digits than its factorization.

81021509974802 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40510754987403.

The product of its (nonzero) digits is 2903040, while the sum is 56.

The spelling of 81021509974802 in words is "eighty-one trillion, twenty-one billion, five hundred nine million, nine hundred seventy-four thousand, eight hundred two".