1021561 has 2 divisors, whose sum is σ = 1021562. Its totient is φ = 1021560.

The previous prime is 1021541. The next prime is 1021571. The reversal of 1021561 is 1651201.

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., 739600 + 281961 = 860^2 + 531^2 .

It is an emirp because it is prime and its reverse (1651201) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1021561 is a prime.

It is an Ulam number.

It is not a weakly prime, because it can be changed into another prime (1021541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510780 + 510781.

It is an arithmetic number, because the mean of its divisors is an integer number (510781).

2^1021561 is an apocalyptic number.

It is an amenable number.

1021561 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021561 is an equidigital number, since it uses as much as digits as its factorization.

1021561 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 60, while the sum is 16.

The square root of 1021561 is about 1010.7230085439. The cubic root of 1021561 is about 100.7135956992.

Adding to 1021561 its reverse (1651201), we get a palindrome (2672762).

The spelling of 1021561 in words is "one million, twenty-one thousand, five hundred sixty-one".