1221646681 has 2 divisors, whose sum is σ = 1221646682. Its totient is φ = 1221646680.

The previous prime is 1221646609. The next prime is 1221646691. The reversal of 1221646681 is 1866461221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1201315600 + 20331081 = 34660^2 + 4509^2 .

It is an emirp because it is prime and its reverse (1866461221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221646681 - 2⁹ = 1221646169 is a prime.

It is a super-2 number, since 2×1221646681² = 2984841226396631522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 1221646681.

It is not a weakly prime, because it can be changed into another prime (1221646691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610823340 + 610823341.

It is an arithmetic number, because the mean of its divisors is an integer number (610823341).

Almost surely, 2^1221646681 is an apocalyptic number.

It is an amenable number.

1221646681 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221646681 is an equidigital number, since it uses as much as digits as its factorization.

1221646681 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27648, while the sum is 37.

The square root of 1221646681 is about 34952.0626143866. The cubic root of 1221646681 is about 1069.0102592646.

The spelling of 1221646681 in words is "one billion, two hundred twenty-one million, six hundred forty-six thousand, six hundred eighty-one".