1221352561 has 32 divisors (see below), whose sum is σ = 1473937920. Its totient is φ = 997401600.

The previous prime is 1221352549. The next prime is 1221352571. The reversal of 1221352561 is 1652531221.

It is not a de Polignac number, because 1221352561 - 2¹⁵ = 1221319793 is a prime.

It is a super-2 number, since 2×1221352561² = 2983404156522517442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1221352501) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 823941 + ... + 825421.

It is an arithmetic number, because the mean of its divisors is an integer number (46060560).

Almost surely, 2^1221352561 is an apocalyptic number.

1221352561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1221352561 is a deficient number, since it is larger than the sum of its proper divisors (252585359).

1221352561 is a wasteful number, since it uses less digits than its factorization.

1221352561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1657.

The product of its digits is 3600, while the sum is 28.

The square root of 1221352561 is about 34947.8548840984. The cubic root of 1221352561 is about 1068.9244618082.

Adding to 1221352561 its reverse (1652531221), we get a palindrome (2873883782).

The spelling of 1221352561 in words is "one billion, two hundred twenty-one million, three hundred fifty-two thousand, five hundred sixty-one".