1221531 has 4 divisors (see below), whose sum is σ = 1628712. Its totient is φ = 814352.

The previous prime is 1221527. The next prime is 1221533. The reversal of 1221531 is 1351221.

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

It is a cyclic number.

It is not a de Polignac number, because 1221531 - 2² = 1221527 is a prime.

It is a super-2 number, since 2×1221531² = 2984275967922, which contains 22 as substring.

It is a D-number.

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 1221531.

It is not an unprimeable number, because it can be changed into a prime (1221533) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 203586 + ... + 203591.

It is an arithmetic number, because the mean of its divisors is an integer number (407178).

2^1221531 is an apocalyptic number.

1221531 is a deficient number, since it is larger than the sum of its proper divisors (407181).

1221531 is an equidigital number, since it uses as much as digits as its factorization.

1221531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 407180.

The product of its digits is 60, while the sum is 15.

The square root of 1221531 is about 1105.2289355604. The cubic root of 1221531 is about 106.8976515717.

Adding to 1221531 its reverse (1351221), we get a palindrome (2572752).

It can be divided in two parts, 12215 and 31, that added together give a triangular number (12246 = T₁₅₆).

The spelling of 1221531 in words is "one million, two hundred twenty-one thousand, five hundred thirty-one".