61591531 has 4 divisors (see below), whose sum is σ = 61717464. Its totient is φ = 61465600.

The previous prime is 61591477. The next prime is 61591549. The reversal of 61591531 is 13519516.

It is a semiprime because it is the product of two primes.

It is a 10-Lehmer number, since φ(61591531) divides (61591531-1)¹⁰.

It is a cyclic number.

It is not a de Polignac number, because 61591531 - 2⁷ = 61591403 is a prime.

It is a super-2 number, since 2×61591531² = 7587033381847922, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 61591493 and 61591502.

It is not an unprimeable number, because it can be changed into a prime (61591031) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 62230 + ... + 63211.

It is an arithmetic number, because the mean of its divisors is an integer number (15429366).

Almost surely, 2^61591531 is an apocalyptic number.

61591531 is a deficient number, since it is larger than the sum of its proper divisors (125933).

61591531 is a wasteful number, since it uses less digits than its factorization.

61591531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125932.

The product of its digits is 4050, while the sum is 31.

The square root of 61591531 is about 7848.0272043361. The cubic root of 61591531 is about 394.9180645092.

The spelling of 61591531 in words is "sixty-one million, five hundred ninety-one thousand, five hundred thirty-one".