1221551 has 2 divisors, whose sum is σ = 1221552. Its totient is φ = 1221550.

The previous prime is 1221541. The next prime is 1221557. The reversal of 1221551 is 1551221.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221551 is a prime.

It is a plaindrome in base 12.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610775 + 610776.

It is an arithmetic number, because the mean of its divisors is an integer number (610776).

2^1221551 is an apocalyptic number.

1221551 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221551 is an equidigital number, since it uses as much as digits as its factorization.

1221551 is an evil number, because the sum of its binary digits is even.

The product of its digits is 100, while the sum is 17.

The square root of 1221551 is about 1105.2379834226. The cubic root of 1221551 is about 106.8982349765.

Adding to 1221551 its reverse (1551221), we get a palindrome (2772772).

The spelling of 1221551 in words is "one million, two hundred twenty-one thousand, five hundred fifty-one".