81629689 has 2 divisors, whose sum is σ = 81629690. Its totient is φ = 81629688.

The previous prime is 81629687. The next prime is 81629707. The reversal of 81629689 is 98692618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 54641664 + 26988025 = 7392^2 + 5195^2 .

It is a cyclic number.

It is not a de Polignac number, because 81629689 - 2¹ = 81629687 is a prime.

It is a super-2 number, since 2×81629689² = 13326812252473442, which contains 22 as substring.

Together with 81629687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (81629683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40814844 + 40814845.

It is an arithmetic number, because the mean of its divisors is an integer number (40814845).

Almost surely, 2^81629689 is an apocalyptic number.

It is an amenable number.

81629689 is a deficient number, since it is larger than the sum of its proper divisors (1).

81629689 is an equidigital number, since it uses as much as digits as its factorization.

81629689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 373248, while the sum is 49.

The square root of 81629689 is about 9034.9149968331. The cubic root of 81629689 is about 433.7931741193.

The spelling of 81629689 in words is "eighty-one million, six hundred twenty-nine thousand, six hundred eighty-nine".