1561170021 has 16 divisors (see below), whose sum is σ = 2168846400. Its totient is φ = 997653888.

The previous prime is 1561170019. The next prime is 1561170097. The reversal of 1561170021 is 1200711651.

It is not a de Polignac number, because 1561170021 - 2¹ = 1561170019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1561169973 and 1561170000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561172021) 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, 52456 + ... + 76641.

It is an arithmetic number, because the mean of its divisors is an integer number (135552900).

Almost surely, 2^1561170021 is an apocalyptic number.

It is an amenable number.

1561170021 is a deficient number, since it is larger than the sum of its proper divisors (607676379).

1561170021 is a wasteful number, since it uses less digits than its factorization.

1561170021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129268.

The product of its (nonzero) digits is 420, while the sum is 24.

The square root of 1561170021 is about 39511.6441191707. The cubic root of 1561170021 is about 1160.0678767753.

Adding to 1561170021 its reverse (1200711651), we get a palindrome (2761881672).

The spelling of 1561170021 in words is "one billion, five hundred sixty-one million, one hundred seventy thousand, twenty-one".