1221640709 has 2 divisors, whose sum is σ = 1221640710. Its totient is φ = 1221640708.

The previous prime is 1221640703. The next prime is 1221640759. The reversal of 1221640709 is 9070461221.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 767013025 + 454627684 = 27695^2 + 21322^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221640709 - 2¹² = 1221636613 is a prime.

It is a Sophie Germain 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 (1221640703) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610820354 + 610820355.

It is an arithmetic number, because the mean of its divisors is an integer number (610820355).

Almost surely, 2^1221640709 is an apocalyptic number.

It is an amenable number.

1221640709 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221640709 is an equidigital number, since it uses as much as digits as its factorization.

1221640709 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6048, while the sum is 32.

The square root of 1221640709 is about 34951.9771829864. The cubic root of 1221640709 is about 1069.0085173153.

It can be divided in two parts, 12216 and 40709, that added together give a palindrome (52925).

The spelling of 1221640709 in words is "one billion, two hundred twenty-one million, six hundred forty thousand, seven hundred nine".