81609629 has 2 divisors, whose sum is σ = 81609630. Its totient is φ = 81609628.

The previous prime is 81609623. The next prime is 81609631. The reversal of 81609629 is 92690618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73188025 + 8421604 = 8555^2 + 2902^2 .

It is a cyclic number.

It is not a de Polignac number, because 81609629 - 2⁴ = 81609613 is a prime.

Together with 81609631, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81609623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40804814 + 40804815.

It is an arithmetic number, because the mean of its divisors is an integer number (40804815).

Almost surely, 2^81609629 is an apocalyptic number.

It is an amenable number.

81609629 is a deficient number, since it is larger than the sum of its proper divisors (1).

81609629 is an equidigital number, since it uses as much as digits as its factorization.

81609629 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 46656, while the sum is 41.

The square root of 81609629 is about 9033.8047908951. The cubic root of 81609629 is about 433.7576371961.

The spelling of 81609629 in words is "eighty-one million, six hundred nine thousand, six hundred twenty-nine".