1516221561 has 4 divisors (see below), whose sum is σ = 2021628752. Its totient is φ = 1010814372.

The previous prime is 1516221547. The next prime is 1516221661. The reversal of 1516221561 is 1651226151.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1651226151 = 3 ⋅550408717.

It is not a de Polignac number, because 1516221561 - 2¹⁷ = 1516090489 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1516221521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 252703591 + ... + 252703596.

It is an arithmetic number, because the mean of its divisors is an integer number (505407188).

Almost surely, 2^1516221561 is an apocalyptic number.

It is an amenable number.

1516221561 is a deficient number, since it is larger than the sum of its proper divisors (505407191).

1516221561 is an equidigital number, since it uses as much as digits as its factorization.

1516221561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 505407190.

The product of its digits is 3600, while the sum is 30.

The square root of 1516221561 is about 38938.6897699448. The cubic root of 1516221561 is about 1148.8259122509.

The spelling of 1516221561 in words is "one billion, five hundred sixteen million, two hundred twenty-one thousand, five hundred sixty-one".