81611389 has 2 divisors, whose sum is σ = 81611390. Its totient is φ = 81611388.

The previous prime is 81611363. The next prime is 81611393. The reversal of 81611389 is 98311618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73102500 + 8508889 = 8550^2 + 2917^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81611389 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 (81614389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40805694 + 40805695.

It is an arithmetic number, because the mean of its divisors is an integer number (40805695).

Almost surely, 2^81611389 is an apocalyptic number.

It is an amenable number.

81611389 is a deficient number, since it is larger than the sum of its proper divisors (1).

81611389 is an equidigital number, since it uses as much as digits as its factorization.

81611389 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 37.

The square root of 81611389 is about 9033.9022022601. The cubic root of 81611389 is about 433.7607553247.

The spelling of 81611389 in words is "eighty-one million, six hundred eleven thousand, three hundred eighty-nine".