1221220061 has 4 divisors (see below), whose sum is σ = 1241240124. Its totient is φ = 1201200000.

The previous prime is 1221220057. The next prime is 1221220069. The reversal of 1221220061 is 1600221221.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 306460036 + 914760025 = 17506^2 + 30245^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221220061 - 2² = 1221220057 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 (1221220069) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10009940 + ... + 10010061.

It is an arithmetic number, because the mean of its divisors is an integer number (310310031).

Almost surely, 2^1221220061 is an apocalyptic number.

It is an amenable number.

1221220061 is a deficient number, since it is larger than the sum of its proper divisors (20020063).

1221220061 is an equidigital number, since it uses as much as digits as its factorization.

1221220061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20020062.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 1221220061 is about 34945.9591512381. The cubic root of 1221220061 is about 1068.8858058629.

Adding to 1221220061 its reverse (1600221221), we get a palindrome (2821441282).

The spelling of 1221220061 in words is "one billion, two hundred twenty-one million, two hundred twenty thousand, sixty-one".