11951561 has 4 divisors (see below), whose sum is σ = 12654612. Its totient is φ = 11248512.

The previous prime is 11951557. The next prime is 11951591. The reversal of 11951561 is 16515911.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 16515911 = 739 ⋅22349.

It can be written as a sum of positive squares in 2 ways, for example, as 5290000 + 6661561 = 2300^2 + 2581^2 .

It is a cyclic number.

It is not a de Polignac number, because 11951561 - 2² = 11951557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (11951531) 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, 351500 + ... + 351533.

It is an arithmetic number, because the mean of its divisors is an integer number (3163653).

Almost surely, 2^11951561 is an apocalyptic number.

It is an amenable number.

11951561 is a deficient number, since it is larger than the sum of its proper divisors (703051).

11951561 is an equidigital number, since it uses as much as digits as its factorization.

11951561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 703050.

The product of its digits is 1350, while the sum is 29.

The square root of 11951561 is about 3457.1029779282. The cubic root of 11951561 is about 228.6343841280.

The spelling of 11951561 in words is "eleven million, nine hundred fifty-one thousand, five hundred sixty-one".