691878097 has 2 divisors, whose sum is σ = 691878098. Its totient is φ = 691878096.

The previous prime is 691878071. The next prime is 691878137. The reversal of 691878097 is 790878196.

691878097 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 577152576 + 114725521 = 24024^2 + 10711^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691878097 is a prime.

It is a super-2 number, since 2×691878097² = 957390602216682818, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (691878007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345939048 + 345939049.

It is an arithmetic number, because the mean of its divisors is an integer number (345939049).

Almost surely, 2^691878097 is an apocalyptic number.

It is an amenable number.

691878097 is a deficient number, since it is larger than the sum of its proper divisors (1).

691878097 is an equidigital number, since it uses as much as digits as its factorization.

691878097 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1524096, while the sum is 55.

The square root of 691878097 is about 26303.5757455141. The cubic root of 691878097 is about 884.4566006722.

Subtracting 691878097 from its reverse (790878196), we obtain a palindrome (99000099).

It can be divided in two parts, 69187 and 8097, that added together give a square (77284 = 278²).

The spelling of 691878097 in words is "six hundred ninety-one million, eight hundred seventy-eight thousand, ninety-seven".