1221201001621 has 2 divisors, whose sum is σ = 1221201001622. Its totient is φ = 1221201001620.

The previous prime is 1221201001589. The next prime is 1221201001627. The reversal of 1221201001621 is 1261001021221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 728102117521 + 493098884100 = 853289^2 + 702210^2 .

It is an emirp because it is prime and its reverse (1261001021221) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1221201001621 - 2⁵ = 1221201001589 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221201001627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610600500810 + 610600500811.

It is an arithmetic number, because the mean of its divisors is an integer number (610600500811).

Almost surely, 2^{1221201001621} is an apocalyptic number.

It is an amenable number.

1221201001621 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221201001621 is an equidigital number, since it uses as much as digits as its factorization.

1221201001621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 96, while the sum is 19.

Adding to 1221201001621 its reverse (1261001021221), we get a palindrome (2482202022842).

The spelling of 1221201001621 in words is "one trillion, two hundred twenty-one billion, two hundred one million, one thousand, six hundred twenty-one".