615561 has 4 divisors (see below), whose sum is σ = 820752. Its totient is φ = 410372.

The previous prime is 615557. The next prime is 615577. The reversal of 615561 is 165516.

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 615561 - 2² = 615557 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (615521) 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, 102591 + ... + 102596.

It is an arithmetic number, because the mean of its divisors is an integer number (205188).

2⁶¹⁵⁵⁶¹ is an apocalyptic number.

It is an amenable number.

615561 is a deficient number, since it is larger than the sum of its proper divisors (205191).

615561 is a wasteful number, since it uses less digits than its factorization.

615561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 205190.

The product of its digits is 900, while the sum is 24.

The square root of 615561 is about 784.5769560725. The cubic root of 615561 is about 85.0661998705.

It can be divided in two parts, 6155 and 61, that added together give a triangular number (6216 = T₁₁₁).

The spelling of 615561 in words is "six hundred fifteen thousand, five hundred sixty-one".