81021764 has 6 divisors (see below), whose sum is σ = 141788094. Its totient is φ = 40510880.

The previous prime is 81021701. The next prime is 81021767. The reversal of 81021764 is 46712018.

It can be written as a sum of positive squares in only one way, i.e., 67108864 + 13912900 = 8192^2 + 3730^2 .

It is not an unprimeable number, because it can be changed into a prime (81021767) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10127717 + ... + 10127724.

It is an arithmetic number, because the mean of its divisors is an integer number (23631349).

Almost surely, 2^81021764 is an apocalyptic number.

It is an amenable number.

81021764 is a deficient number, since it is larger than the sum of its proper divisors (60766330).

81021764 is a wasteful number, since it uses less digits than its factorization.

81021764 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20255445 (or 20255443 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 29.

The square root of 81021764 is about 9001.2090299026. The cubic root of 81021764 is about 432.7136196215.

The spelling of 81021764 in words is "eighty-one million, twenty-one thousand, seven hundred sixty-four".