1221505451251 has 4 divisors (see below), whose sum is σ = 1238238402712. Its totient is φ = 1204772499792.

The previous prime is 1221505451233. The next prime is 1221505451273. The reversal of 1221505451251 is 1521545051221.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221505451251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1221505451281) 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, 8366475621 + ... + 8366475766.

It is an arithmetic number, because the mean of its divisors is an integer number (309559600678).

Almost surely, 2^{1221505451251} is an apocalyptic number.

1221505451251 is a deficient number, since it is larger than the sum of its proper divisors (16732951461).

1221505451251 is an equidigital number, since it uses as much as digits as its factorization.

1221505451251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16732951460.

The product of its (nonzero) digits is 20000, while the sum is 34.

The spelling of 1221505451251 in words is "one trillion, two hundred twenty-one billion, five hundred five million, four hundred fifty-one thousand, two hundred fifty-one".