1561522220 has 48 divisors (see below), whose sum is σ = 3471884640. Its totient is φ = 588289536.

The previous prime is 1561522217. The next prime is 1561522223. The reversal of 1561522220 is 222251651.

It is an interprime number because it is at equal distance from previous prime (1561522217) and next prime (1561522223).

It is a self number, because there is not a number n which added to its sum of digits gives 1561522220.

It is not an unprimeable number, because it can be changed into a prime (1561522223) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53864 + ... + 77616.

It is an arithmetic number, because the mean of its divisors is an integer number (72330930).

Almost surely, 2^1561522220 is an apocalyptic number.

1561522220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1561522220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1735942320).

1561522220 is an abundant number, since it is smaller than the sum of its proper divisors (1910362420).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1561522220 is a wasteful number, since it uses less digits than its factorization.

1561522220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23954 (or 23952 counting only the distinct ones).

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 1561522220 is about 39516.1007691801. The cubic root of 1561522220 is about 1160.1551070833.

Adding to 1561522220 its reverse (222251651), we get a palindrome (1783773871).

The spelling of 1561522220 in words is "one billion, five hundred sixty-one million, five hundred twenty-two thousand, two hundred twenty".