1221175171621 has 4 divisors (see below), whose sum is σ = 1221178388332. Its totient is φ = 1221171954912.

The previous prime is 1221175171613. The next prime is 1221175171639. The reversal of 1221175171621 is 1261715711221.

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 680111946721 + 541063224900 = 824689^2 + 735570^2 .

It is a cyclic number.

It is not a de Polignac number, because 1221175171621 - 2³ = 1221175171613 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 (1221175171651) 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, 948726 + ... + 1828231.

It is an arithmetic number, because the mean of its divisors is an integer number (305294597083).

Almost surely, 2^{1221175171621} is an apocalyptic number.

It is an amenable number.

1221175171621 is a deficient number, since it is larger than the sum of its proper divisors (3216711).

1221175171621 is an equidigital number, since it uses as much as digits as its factorization.

1221175171621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3216710.

The product of its digits is 11760, while the sum is 37.

The spelling of 1221175171621 in words is "one trillion, two hundred twenty-one billion, one hundred seventy-five million, one hundred seventy-one thousand, six hundred twenty-one".