1977667781 has 2 divisors, whose sum is σ = 1977667782. Its totient is φ = 1977667780.

The previous prime is 1977667777. The next prime is 1977667793. The reversal of 1977667781 is 1877667791.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1839981025 + 137686756 = 42895^2 + 11734^2 .

It is a cyclic number.

It is not a de Polignac number, because 1977667781 - 2² = 1977667777 is a prime.

It is a super-2 number, since 2×1977667781² = 7822339704010927922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1977667781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1977667981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 988833890 + 988833891.

It is an arithmetic number, because the mean of its divisors is an integer number (988833891).

Almost surely, 2^1977667781 is an apocalyptic number.

It is an amenable number.

1977667781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1977667781 is an equidigital number, since it uses as much as digits as its factorization.

1977667781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6223392, while the sum is 59.

The square root of 1977667781 is about 44470.9768388328. The cubic root of 1977667781 is about 1255.2140142845.

The spelling of 1977667781 in words is "one billion, nine hundred seventy-seven million, six hundred sixty-seven thousand, seven hundred eighty-one".