61509 has 16 divisors (see below), whose sum is σ = 97920. Its totient is φ = 33600.

The previous prime is 61507. The next prime is 61511. The reversal of 61509 is 90516.

It is an interprime number because it is at equal distance from previous prime (61507) and next prime (61511).

It is not a de Polignac number, because 61509 - 2¹ = 61507 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a plaindrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (61507) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 559 + ... + 659.

It is an arithmetic number, because the mean of its divisors is an integer number (6120).

2⁶¹⁵⁰⁹ is an apocalyptic number.

It is an amenable number.

61509 is a deficient number, since it is larger than the sum of its proper divisors (36411).

61509 is a wasteful number, since it uses less digits than its factorization.

61509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140.

The product of its (nonzero) digits is 270, while the sum is 21.

The square root of 61509 is about 248.0100804403. The cubic root of 61509 is about 39.4741592457.

The spelling of 61509 in words is "sixty-one thousand, five hundred nine".