71531 has 4 divisors (see below), whose sum is σ = 72072. Its totient is φ = 70992.

The previous prime is 71527. The next prime is 71537. The reversal of 71531 is 13517.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 13517 = 7 ⋅1931.

It is a cyclic number.

It is not a de Polignac number, because 71531 - 2² = 71527 is a prime.

It is a super-2 number, since 2×71531² = 10233367922, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (71537) 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, 80 + ... + 386.

It is an arithmetic number, because the mean of its divisors is an integer number (18018).

2⁷¹⁵³¹ is an apocalyptic number.

71531 is a deficient number, since it is larger than the sum of its proper divisors (541).

71531 is a wasteful number, since it uses less digits than its factorization.

71531 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 540.

The product of its digits is 105, while the sum is 17.

The square root of 71531 is about 267.4527995741. The cubic root of 71531 is about 41.5111500499.

The spelling of 71531 in words is "seventy-one thousand, five hundred thirty-one".