81909887 has 2 divisors, whose sum is σ = 81909888. Its totient is φ = 81909886.

The previous prime is 81909881. The next prime is 81909899. The reversal of 81909887 is 78890918.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81909887 - 2⁴ = 81909871 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81909881) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40954943 + 40954944.

It is an arithmetic number, because the mean of its divisors is an integer number (40954944).

Almost surely, 2^81909887 is an apocalyptic number.

81909887 is a deficient number, since it is larger than the sum of its proper divisors (1).

81909887 is an equidigital number, since it uses as much as digits as its factorization.

81909887 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 290304, while the sum is 50.

The square root of 81909887 is about 9050.4081123450. The cubic root of 81909887 is about 434.2889462365.

The spelling of 81909887 in words is "eighty-one million, nine hundred nine thousand, eight hundred eighty-seven".