4001561 has 2 divisors, whose sum is σ = 4001562. Its totient is φ = 4001560.

The previous prime is 4001551. The next prime is 4001567. The reversal of 4001561 is 1651004.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 3705625 + 295936 = 1925^2 + 544^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-4001561 is a prime.

It is a super-3 number, since 3×4001561³ (a number of 21 digits) contains 333 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (4001567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2000780 + 2000781.

It is an arithmetic number, because the mean of its divisors is an integer number (2000781).

Almost surely, 2^4001561 is an apocalyptic number.

It is an amenable number.

4001561 is a deficient number, since it is larger than the sum of its proper divisors (1).

4001561 is an equidigital number, since it uses as much as digits as its factorization.

4001561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 4001561 is about 2000.3902119337. The cubic root of 4001561 is about 158.7607519533.

Adding to 4001561 its reverse (1651004), we get a palindrome (5652565).

The spelling of 4001561 in words is "four million, one thousand, five hundred sixty-one".