81947090 has 16 divisors (see below), whose sum is σ = 147680280. Its totient is φ = 32739840.

The previous prime is 81947087. The next prime is 81947093. The reversal of 81947090 is 9074918.

It is an interprime number because it is at equal distance from previous prime (81947087) and next prime (81947093).

It can be written as a sum of positive squares in 4 ways, for example, as 46389721 + 35557369 = 6811^2 + 5963^2 .

It is not an unprimeable number, because it can be changed into a prime (81947093) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4880 + ... + 13700.

Almost surely, 2^81947090 is an apocalyptic number.

81947090 is a deficient number, since it is larger than the sum of its proper divisors (65733190).

81947090 is a wasteful number, since it uses less digits than its factorization.

81947090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9757.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 81947090 is about 9052.4632006985. The cubic root of 81947090 is about 434.3546867992.

The spelling of 81947090 in words is "eighty-one million, nine hundred forty-seven thousand, ninety".