691944791 has 4 divisors (see below), whose sum is σ = 692237784. Its totient is φ = 691651800.

The previous prime is 691944779. The next prime is 691944821. The reversal of 691944791 is 197449196.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 691944791 - 2¹⁸ = 691682647 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691944731) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 142925 + ... + 147686.

It is an arithmetic number, because the mean of its divisors is an integer number (173059446).

Almost surely, 2^691944791 is an apocalyptic number.

691944791 is a deficient number, since it is larger than the sum of its proper divisors (292993).

691944791 is a wasteful number, since it uses less digits than its factorization.

691944791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 292992.

The product of its digits is 489888, while the sum is 50.

The square root of 691944791 is about 26304.8434893652. The cubic root of 691944791 is about 884.4850189989.

The spelling of 691944791 in words is "six hundred ninety-one million, nine hundred forty-four thousand, seven hundred ninety-one".