1561516221 has 8 divisors (see below), whose sum is σ = 2149183744. Its totient is φ = 1007429760.

The previous prime is 1561516219. The next prime is 1561516259. The reversal of 1561516221 is 1226151651.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1561516221 - 2¹ = 1561516219 is a prime.

It is a super-2 number, since 2×1561516221² = 4876665816892241682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561556221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8395156 + ... + 8395341.

It is an arithmetic number, because the mean of its divisors is an integer number (268647968).

Almost surely, 2^1561516221 is an apocalyptic number.

It is an amenable number.

1561516221 is a deficient number, since it is larger than the sum of its proper divisors (587667523).

1561516221 is a wasteful number, since it uses less digits than its factorization.

1561516221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16790531.

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

The square root of 1561516221 is about 39516.0248633387. The cubic root of 1561516221 is about 1160.1536214006.

Adding to 1561516221 its reverse (1226151651), we get a palindrome (2787667872).

The spelling of 1561516221 in words is "one billion, five hundred sixty-one million, five hundred sixteen thousand, two hundred twenty-one".