81377729 has 2 divisors, whose sum is σ = 81377730. Its totient is φ = 81377728.

The previous prime is 81377713. The next prime is 81377753. The reversal of 81377729 is 92777318.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80066704 + 1311025 = 8948^2 + 1145^2 .

It is a cyclic number.

It is not a de Polignac number, because 81377729 - 2⁴ = 81377713 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81377729.

It is not a weakly prime, because it can be changed into another prime (81377029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40688864 + 40688865.

It is an arithmetic number, because the mean of its divisors is an integer number (40688865).

Almost surely, 2^81377729 is an apocalyptic number.

It is an amenable number.

81377729 is a deficient number, since it is larger than the sum of its proper divisors (1).

81377729 is an equidigital number, since it uses as much as digits as its factorization.

81377729 is an evil number, because the sum of its binary digits is even.

The product of its digits is 148176, while the sum is 44.

The square root of 81377729 is about 9020.9605364396. The cubic root of 81377729 is about 433.3463955957.

The spelling of 81377729 in words is "eighty-one million, three hundred seventy-seven thousand, seven hundred twenty-nine".