1221015517 has 2 divisors, whose sum is σ = 1221015518. Its totient is φ = 1221015516.

The previous prime is 1221015461. The next prime is 1221015541. The reversal of 1221015517 is 7155101221.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 708943876 + 512071641 = 26626^2 + 22629^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1221015517 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1221015491 and 1221015500.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1221015557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 610507758 + 610507759.

It is an arithmetic number, because the mean of its divisors is an integer number (610507759).

Almost surely, 2^1221015517 is an apocalyptic number.

It is an amenable number.

1221015517 is a deficient number, since it is larger than the sum of its proper divisors (1).

1221015517 is an equidigital number, since it uses as much as digits as its factorization.

1221015517 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 700, while the sum is 25.

The square root of 1221015517 is about 34943.0324528367. The cubic root of 1221015517 is about 1068.8261260960.

Adding to 1221015517 its reverse (7155101221), we get a palindrome (8376116738).

The spelling of 1221015517 in words is "one billion, two hundred twenty-one million, fifteen thousand, five hundred seventeen".