1561511001 has 16 divisors (see below), whose sum is σ = 2135587520. Its totient is φ = 1014534720.

The previous prime is 1561510997. The next prime is 1561511087. The reversal of 1561511001 is 1001151651.

It is a happy number.

It is not a de Polignac number, because 1561511001 - 2² = 1561510997 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561511201) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19195 + ... + 59088.

It is an arithmetic number, because the mean of its divisors is an integer number (133474220).

Almost surely, 2^1561511001 is an apocalyptic number.

It is an amenable number.

1561511001 is a deficient number, since it is larger than the sum of its proper divisors (574076519).

1561511001 is a wasteful number, since it uses less digits than its factorization.

1561511001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 78456.

The product of its (nonzero) digits is 150, while the sum is 21.

The square root of 1561511001 is about 39515.9588141298. The cubic root of 1561511001 is about 1160.1523286382.

Adding to 1561511001 its reverse (1001151651), we get a palindrome (2562662652).

The spelling of 1561511001 in words is "one billion, five hundred sixty-one million, five hundred eleven thousand, one".