1561223011 has 4 divisors (see below), whose sum is σ = 1561303072. Its totient is φ = 1561142952.

The previous prime is 1561223009. The next prime is 1561223057. The reversal of 1561223011 is 1103221651.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 1103221651 = 7 ⋅157603093.

It is a cyclic number.

It is not a de Polignac number, because 1561223011 - 2¹ = 1561223009 is a prime.

It is a super-2 number, since 2×1561223011² = 4874834580151812242, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561223071) 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, 10390 + ... + 56836.

It is an arithmetic number, because the mean of its divisors is an integer number (390325768).

Almost surely, 2^1561223011 is an apocalyptic number.

1561223011 is a deficient number, since it is larger than the sum of its proper divisors (80061).

1561223011 is an equidigital number, since it uses as much as digits as its factorization.

1561223011 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80060.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 1561223011 is about 39512.3146753009. The cubic root of 1561223011 is about 1160.0810018248.

Adding to 1561223011 its reverse (1103221651), we get a palindrome (2664444662).

The spelling of 1561223011 in words is "one billion, five hundred sixty-one million, two hundred twenty-three thousand, eleven".