691951 has 16 divisors (see below), whose sum is σ = 822528. Its totient is φ = 576000.

The previous prime is 691949. The next prime is 691973. The reversal of 691951 is 159196.

It is a 9-Lehmer number, since φ(691951) divides (691951-1)⁹.

It is a cyclic number.

It is not a de Polignac number, because 691951 - 2¹ = 691949 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

Its product of digits (2430) is a multiple of the sum of its prime divisors (162).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691921) 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 15 ways as a sum of consecutive naturals, for example, 6801 + ... + 6901.

It is an arithmetic number, because the mean of its divisors is an integer number (51408).

2⁶⁹¹⁹⁵¹ is an apocalyptic number.

691951 is a deficient number, since it is larger than the sum of its proper divisors (130577).

691951 is a wasteful number, since it uses less digits than its factorization.

691951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 162.

The product of its digits is 2430, while the sum is 31.

The square root of 691951 is about 831.8359213210. The cubic root of 691951 is about 88.4487664562.

It can be divided in two parts, 69195 and 1, that added together give a palindrome (69196).

The spelling of 691951 in words is "six hundred ninety-one thousand, nine hundred fifty-one".