1221511515251 has 8 divisors (see below), whose sum is σ = 1239765393360. Its totient is φ = 1203258295008.

The previous prime is 1221511515247. The next prime is 1221511515317. The reversal of 1221511515251 is 1525151151221.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1221511515251 - 2² = 1221511515247 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221511505251) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4600325 + ... + 4858601.

It is an arithmetic number, because the mean of its divisors is an integer number (154970674170).

Almost surely, 2^{1221511515251} is an apocalyptic number.

1221511515251 is a deficient number, since it is larger than the sum of its proper divisors (18253878109).

1221511515251 is an equidigital number, since it uses as much as digits as its factorization.

1221511515251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 328933.

The product of its digits is 5000, while the sum is 32.

Adding to 1221511515251 its reverse (1525151151221), we get a palindrome (2746662666472).

The spelling of 1221511515251 in words is "one trillion, two hundred twenty-one billion, five hundred eleven million, five hundred fifteen thousand, two hundred fifty-one".