77971661 has 2 divisors, whose sum is σ = 77971662. Its totient is φ = 77971660.

The previous prime is 77971651. The next prime is 77971681. The reversal of 77971661 is 16617977.

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., 64096036 + 13875625 = 8006^2 + 3725^2 .

It is an emirp because it is prime and its reverse (16617977) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77971661 is a prime.

It is a super-3 number, since 3×77971661³ (a number of 25 digits) contains 333 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77971631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38985830 + 38985831.

It is an arithmetic number, because the mean of its divisors is an integer number (38985831).

Almost surely, 2^77971661 is an apocalyptic number.

It is an amenable number.

77971661 is a deficient number, since it is larger than the sum of its proper divisors (1).

77971661 is an equidigital number, since it uses as much as digits as its factorization.

77971661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 111132, while the sum is 44.

The square root of 77971661 is about 8830.1563406318. The cubic root of 77971661 is about 427.2141170838.

The spelling of 77971661 in words is "seventy-seven million, nine hundred seventy-one thousand, six hundred sixty-one".