77281661 has 2 divisors, whose sum is σ = 77281662. Its totient is φ = 77281660.

The previous prime is 77281657. The next prime is 77281691. The reversal of 77281661 is 16618277.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 73633561 + 3648100 = 8581^2 + 1910^2 .

It is a cyclic number.

It is not a de Polignac number, because 77281661 - 2² = 77281657 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77281601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38640830 + 38640831.

It is an arithmetic number, because the mean of its divisors is an integer number (38640831).

Almost surely, 2^77281661 is an apocalyptic number.

It is an amenable number.

77281661 is a deficient number, since it is larger than the sum of its proper divisors (1).

77281661 is an equidigital number, since it uses as much as digits as its factorization.

77281661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 28224, while the sum is 38.

The square root of 77281661 is about 8790.9988624729. The cubic root of 77281661 is about 425.9501896106.

The spelling of 77281661 in words is "seventy-seven million, two hundred eighty-one thousand, six hundred sixty-one".