81609371 has 2 divisors, whose sum is σ = 81609372. Its totient is φ = 81609370.

The previous prime is 81609337. The next prime is 81609377. The reversal of 81609371 is 17390618.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81609371 - 2²² = 77415067 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81609377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40804685 + 40804686.

It is an arithmetic number, because the mean of its divisors is an integer number (40804686).

Almost surely, 2^81609371 is an apocalyptic number.

81609371 is a deficient number, since it is larger than the sum of its proper divisors (1).

81609371 is an equidigital number, since it uses as much as digits as its factorization.

81609371 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 81609371 is about 9033.7905111863. The cubic root of 81609371 is about 433.7571801030.

Adding to 81609371 its reverse (17390618), we get a palindrome (98999989).

The spelling of 81609371 in words is "eighty-one million, six hundred nine thousand, three hundred seventy-one".