781561 has 8 divisors (see below), whose sum is σ = 859104. Its totient is φ = 705120.

The previous prime is 781559. The next prime is 781567. The reversal of 781561 is 165187.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 781561 - 2¹ = 781559 is a prime.

It is a super-2 number, since 2×781561² = 1221675193442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (781567) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2341 + ... + 2653.

It is an arithmetic number, because the mean of its divisors is an integer number (107388).

2⁷⁸¹⁵⁶¹ is an apocalyptic number.

It is an amenable number.

781561 is a deficient number, since it is larger than the sum of its proper divisors (77543).

781561 is a wasteful number, since it uses less digits than its factorization.

781561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 551.

The product of its digits is 1680, while the sum is 28.

The square root of 781561 is about 884.0593871455. The cubic root of 781561 is about 92.1130070052.

The spelling of 781561 in words is "seven hundred eighty-one thousand, five hundred sixty-one".