1215438211721 has 4 divisors (see below), whose sum is σ = 1218409943700. Its totient is φ = 1212466479744.

The previous prime is 1215438211703. The next prime is 1215438211733. The reversal of 1215438211721 is 1271128345121.

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 717009271696 + 498428940025 = 846764^2 + 705995^2 .

It is a cyclic number.

It is not a de Polignac number, because 1215438211721 - 2³⁴ = 1198258342537 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1215438211751) 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, 1485865376 + ... + 1485866193.

It is an arithmetic number, because the mean of its divisors is an integer number (304602485925).

Almost surely, 2^{1215438211721} is an apocalyptic number.

It is an amenable number.

1215438211721 is a deficient number, since it is larger than the sum of its proper divisors (2971731979).

1215438211721 is an equidigital number, since it uses as much as digits as its factorization.

1215438211721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2971731978.

The product of its digits is 26880, while the sum is 38.

The spelling of 1215438211721 in words is "one trillion, two hundred fifteen billion, four hundred thirty-eight million, two hundred eleven thousand, seven hundred twenty-one".