691521 has 4 divisors (see below), whose sum is σ = 922032. Its totient is φ = 461012.

The previous prime is 691499. The next prime is 691531. The reversal of 691521 is 125196.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 691521 - 2⁵ = 691489 is a prime.

It is a D-number.

It is a Curzon number.

691521 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 691491 and 691500.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 691521.

It is not an unprimeable number, because it can be changed into a prime (691531) 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, 115251 + ... + 115256.

It is an arithmetic number, because the mean of its divisors is an integer number (230508).

2⁶⁹¹⁵²¹ is an apocalyptic number.

It is an amenable number.

691521 is a deficient number, since it is larger than the sum of its proper divisors (230511).

691521 is a wasteful number, since it uses less digits than its factorization.

691521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230510.

The product of its digits is 540, while the sum is 24.

The square root of 691521 is about 831.5774167208. The cubic root of 691521 is about 88.4304410495.

The spelling of 691521 in words is "six hundred ninety-one thousand, five hundred twenty-one".