691849505 has 4 divisors (see below), whose sum is σ = 830219412. Its totient is φ = 553479600.

The previous prime is 691849471. The next prime is 691849507. The reversal of 691849505 is 505948196.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 359443681 + 332405824 = 18959^2 + 18232^2 .

It is not a de Polignac number, because 691849505 - 2⁶ = 691849441 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 691849505.

It is not an unprimeable number, because it can be changed into a prime (691849507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 69184946 + ... + 69184955.

It is an arithmetic number, because the mean of its divisors is an integer number (207554853).

Almost surely, 2^691849505 is an apocalyptic number.

It is an amenable number.

691849505 is a deficient number, since it is larger than the sum of its proper divisors (138369907).

691849505 is a wasteful number, since it uses less digits than its factorization.

691849505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 138369906.

The product of its (nonzero) digits is 388800, while the sum is 47.

The square root of 691849505 is about 26303.0322396487. The cubic root of 691849505 is about 884.4444170561. Note that the first 4 decimals are identical.

The spelling of 691849505 in words is "six hundred ninety-one million, eight hundred forty-nine thousand, five hundred five".