1213512721 has 2 divisors, whose sum is σ = 1213512722. Its totient is φ = 1213512720.

The previous prime is 1213512667. The next prime is 1213512733. The reversal of 1213512721 is 1272153121.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1106493696 + 107019025 = 33264^2 + 10345^2 .

It is a cyclic number.

It is not a de Polignac number, because 1213512721 - 2¹³ = 1213504529 is a prime.

It is a super-2 number, since 2×1213512721² = 2945226248057647682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1213522721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 606756360 + 606756361.

It is an arithmetic number, because the mean of its divisors is an integer number (606756361).

Almost surely, 2^1213512721 is an apocalyptic number.

It is an amenable number.

1213512721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1213512721 is an equidigital number, since it uses as much as digits as its factorization.

1213512721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 840, while the sum is 25.

The square root of 1213512721 is about 34835.5094838586. The cubic root of 1213512721 is about 1066.6324149917.

Adding to 1213512721 its reverse (1272153121), we get a palindrome (2485665842).

The spelling of 1213512721 in words is "one billion, two hundred thirteen million, five hundred twelve thousand, seven hundred twenty-one".