81870641 has 2 divisors, whose sum is σ = 81870642. Its totient is φ = 81870640.

The previous prime is 81870577. The next prime is 81870643. The reversal of 81870641 is 14607818.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 71656225 + 10214416 = 8465^2 + 3196^2 .

It is a cyclic number.

It is not a de Polignac number, because 81870641 - 2⁶ = 81870577 is a prime.

Together with 81870643, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81870643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40935320 + 40935321.

It is an arithmetic number, because the mean of its divisors is an integer number (40935321).

Almost surely, 2^81870641 is an apocalyptic number.

It is an amenable number.

81870641 is a deficient number, since it is larger than the sum of its proper divisors (1).

81870641 is an equidigital number, since it uses as much as digits as its factorization.

81870641 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10752, while the sum is 35.

The square root of 81870641 is about 9048.2396630505. The cubic root of 81870641 is about 434.2195739565.

The spelling of 81870641 in words is "eighty-one million, eight hundred seventy thousand, six hundred forty-one".