1221653591 has 2 divisors, whose sum is σ = 1221653592. Its totient is φ = 1221653590.

The previous prime is 1221653567. The next prime is 1221653603. The reversal of 1221653591 is 1953561221.

It is a strong prime.

It is an emirp because it is prime and its reverse (1953561221) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221653591 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221653291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610826795 + 610826796.

It is an arithmetic number, because the mean of its divisors is an integer number (610826796).

Almost surely, 2^1221653591 is an apocalyptic number.

1221653591 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221653591 is an equidigital number, since it uses as much as digits as its factorization.

1221653591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 16200, while the sum is 35.

The square root of 1221653591 is about 34952.1614639209. The cubic root of 1221653591 is about 1069.0122748084.

The spelling of 1221653591 in words is "one billion, two hundred twenty-one million, six hundred fifty-three thousand, five hundred ninety-one".