521731 has 8 divisors (see below), whose sum is σ = 605024. Its totient is φ = 440640.

The previous prime is 521723. The next prime is 521743. The reversal of 521731 is 137125.

521731 = 270² + 271² + ... + 276².

521731 is a nontrivial binomial coefficient, being equal to C(1022, 2).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a 6-Lehmer number, since φ(521731) divides (521731-1)⁶.

It is a cyclic number.

It is not a de Polignac number, because 521731 - 2³ = 521723 is a prime.

It is a super-2 number, since 2×521731² = 544406472722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 521699 and 521708.

It is not an unprimeable number, because it can be changed into a prime (521791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1 + ... + 1021.

It is an arithmetic number, because the mean of its divisors is an integer number (75628).

2⁵²¹⁷³¹ is an apocalyptic number.

521731 is the 1021-st triangular number and also the 511-st hexagonal number.

521731 is the 341-st centered nonagonal number.

521731 is a deficient number, since it is larger than the sum of its proper divisors (83293).

521731 is a wasteful number, since it uses less digits than its factorization.

521731 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1101.

The product of its digits is 210, while the sum is 19.

The square root of 521731 is about 722.3094904541. The cubic root of 521731 is about 80.5036455276.

Adding to 521731 its reverse (137125), we get a palindrome (658856).

It can be divided in two parts, 5 and 21731, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 521731 in words is "five hundred twenty-one thousand, seven hundred thirty-one".