1021221661 has 4 divisors (see below), whose sum is σ = 1021289500. Its totient is φ = 1021153824.

The previous prime is 1021221653. The next prime is 1021221673. The reversal of 1021221661 is 1661221201.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 953883225 + 67338436 = 30885^2 + 8206^2 .

It is a cyclic number.

It is not a de Polignac number, because 1021221661 - 2³ = 1021221653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1021221961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 96 + ... + 45193.

It is an arithmetic number, because the mean of its divisors is an integer number (255322375).

Almost surely, 2^1021221661 is an apocalyptic number.

It is an amenable number.

1021221661 is a deficient number, since it is larger than the sum of its proper divisors (67839).

1021221661 is an equidigital number, since it uses as much as digits as its factorization.

1021221661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67838.

The product of its (nonzero) digits is 288, while the sum is 22.

The square root of 1021221661 is about 31956.5589668224. The cubic root of 1021221661 is about 1007.0244288646.

Adding to 1021221661 its reverse (1661221201), we get a palindrome (2682442862).

The spelling of 1021221661 in words is "one billion, twenty-one million, two hundred twenty-one thousand, six hundred sixty-one".