691551 has 16 divisors (see below), whose sum is σ = 1171200. Its totient is φ = 395064.

The previous prime is 691531. The next prime is 691553. The reversal of 691551 is 155196.

It is not a de Polignac number, because 691551 - 2¹⁵ = 658783 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691551.

It is not an unprimeable number, because it can be changed into a prime (691553) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1641 + ... + 2018.

It is an arithmetic number, because the mean of its divisors is an integer number (73200).

2⁶⁹¹⁵⁵¹ is an apocalyptic number.

691551 is a deficient number, since it is larger than the sum of its proper divisors (479649).

691551 is a wasteful number, since it uses less digits than its factorization.

691551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3675 (or 3669 counting only the distinct ones).

The product of its digits is 1350, while the sum is 27.

The square root of 691551 is about 831.5954545330. The cubic root of 691551 is about 88.4317198127.

The spelling of 691551 in words is "six hundred ninety-one thousand, five hundred fifty-one".