1561621541 has 4 divisors (see below), whose sum is σ = 1562905932. Its totient is φ = 1560337152.

The previous prime is 1561621517. The next prime is 1561621543. The reversal of 1561621541 is 1451261651.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 903904225 + 657717316 = 30065^2 + 25646^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561621541 - 2¹⁰ = 1561620517 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1561621498 and 1561621507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561621543) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 640370 + ... + 642803.

It is an arithmetic number, because the mean of its divisors is an integer number (390726483).

Almost surely, 2^1561621541 is an apocalyptic number.

It is an amenable number.

1561621541 is a deficient number, since it is larger than the sum of its proper divisors (1284391).

1561621541 is a wasteful number, since it uses less digits than its factorization.

1561621541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1284390.

The product of its digits is 7200, while the sum is 32.

The square root of 1561621541 is about 39517.3574647901. The cubic root of 1561621541 is about 1160.1797038775.

The spelling of 1561621541 in words is "one billion, five hundred sixty-one million, six hundred twenty-one thousand, five hundred forty-one".