1021661 has 2 divisors, whose sum is σ = 1021662. Its totient is φ = 1021660.

The previous prime is 1021651. The next prime is 1021663. The reversal of 1021661 is 1661201.

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., 765625 + 256036 = 875^2 + 506^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1021661 is a prime.

It is a Sophie Germain prime.

Together with 1021663, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1021663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 510830 + 510831.

It is an arithmetic number, because the mean of its divisors is an integer number (510831).

2^1021661 is an apocalyptic number.

It is an amenable number.

1021661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1021661 is an equidigital number, since it uses as much as digits as its factorization.

1021661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 1021661 is about 1010.7724768710. The cubic root of 1021661 is about 100.7168818567.

Adding to 1021661 its reverse (1661201), we get a palindrome (2682862).

The spelling of 1021661 in words is "one million, twenty-one thousand, six hundred sixty-one".