1001056561 has 4 divisors (see below), whose sum is σ = 1001562352. Its totient is φ = 1000550772.

The previous prime is 1001056559. The next prime is 1001056579. The reversal of 1001056561 is 1656501001.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1656501001 = 1447 ⋅1144783.

It is a cyclic number.

It is not a de Polignac number, because 1001056561 - 2¹ = 1001056559 is a prime.

It is a super-2 number, since 2×1001056561² = 2004228476642293442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1001056261) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 249915 + ... + 253888.

It is an arithmetic number, because the mean of its divisors is an integer number (250390588).

Almost surely, 2^1001056561 is an apocalyptic number.

It is an amenable number.

1001056561 is a deficient number, since it is larger than the sum of its proper divisors (505791).

1001056561 is an equidigital number, since it uses as much as digits as its factorization.

1001056561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505790.

The product of its (nonzero) digits is 900, while the sum is 25.

The square root of 1001056561 is about 31639.4778876011. The cubic root of 1001056561 is about 1000.3520630371.

Adding to 1001056561 its reverse (1656501001), we get a palindrome (2657557562).

The spelling of 1001056561 in words is "one billion, one million, fifty-six thousand, five hundred sixty-one".