1221322551 has 16 divisors (see below), whose sum is σ = 1737805824. Its totient is φ = 760281984.

The previous prime is 1221322547. The next prime is 1221322561. The reversal of 1221322551 is 1552231221.

It is not a de Polignac number, because 1221322551 - 2² = 1221322547 is a prime.

It is a super-2 number, since 2×1221322551² = 2983257547162295202, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1221322561) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 87805 + ... + 100758.

It is an arithmetic number, because the mean of its divisors is an integer number (108612864).

Almost surely, 2^1221322551 is an apocalyptic number.

1221322551 is a deficient number, since it is larger than the sum of its proper divisors (516483273).

1221322551 is a wasteful number, since it uses less digits than its factorization.

1221322551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 188710.

The product of its digits is 1200, while the sum is 24.

The square root of 1221322551 is about 34947.4255274977. The cubic root of 1221322551 is about 1068.9157068462.

Adding to 1221322551 its reverse (1552231221), we get a palindrome (2773553772).

The spelling of 1221322551 in words is "one billion, two hundred twenty-one million, three hundred twenty-two thousand, five hundred fifty-one".