81538789 has 2 divisors, whose sum is σ = 81538790. Its totient is φ = 81538788.

The previous prime is 81538781. The next prime is 81538801. The reversal of 81538789 is 98783518.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70845889 + 10692900 = 8417^2 + 3270^2 .

It is a cyclic number.

It is not a de Polignac number, because 81538789 - 2³ = 81538781 is a prime.

It is a super-2 number, since 2×81538789² = 13297148223173042, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81538781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40769394 + 40769395.

It is an arithmetic number, because the mean of its divisors is an integer number (40769395).

Almost surely, 2^81538789 is an apocalyptic number.

It is an amenable number.

81538789 is a deficient number, since it is larger than the sum of its proper divisors (1).

81538789 is an equidigital number, since it uses as much as digits as its factorization.

81538789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 49.

The square root of 81538789 is about 9029.8831110929. The cubic root of 81538789 is about 433.6320952860.

The spelling of 81538789 in words is "eighty-one million, five hundred thirty-eight thousand, seven hundred eighty-nine".