4021561 has 2 divisors, whose sum is σ = 4021562. Its totient is φ = 4021560.

The previous prime is 4021543. The next prime is 4021579. The reversal of 4021561 is 1651204.

It is a balanced prime because it is at equal distance from previous prime (4021543) and next prime (4021579).

It can be written as a sum of positive squares in only one way, i.e., 2250000 + 1771561 = 1500^2 + 1331^2 .

It is a cyclic number.

It is not a de Polignac number, because 4021561 - 2⁵ = 4021529 is a prime.

It is not a weakly prime, because it can be changed into another prime (4021531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2010780 + 2010781.

It is an arithmetic number, because the mean of its divisors is an integer number (2010781).

Almost surely, 2^4021561 is an apocalyptic number.

It is an amenable number.

4021561 is a deficient number, since it is larger than the sum of its proper divisors (1).

4021561 is an equidigital number, since it uses as much as digits as its factorization.

4021561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 240, while the sum is 19.

The square root of 4021561 is about 2005.3830058121. The cubic root of 4021561 is about 159.0248105476.

Adding to 4021561 its reverse (1651204), we get a palindrome (5672765).

The spelling of 4021561 in words is "four million, twenty-one thousand, five hundred sixty-one".