990307561 has 4 divisors (see below), whose sum is σ = 1003873492. Its totient is φ = 976741632.

The previous prime is 990307559. The next prime is 990307589. The reversal of 990307561 is 165703099.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165703099 = 41 ⋅4041539.

It can be written as a sum of positive squares in 2 ways, for example, as 682515625 + 307791936 = 26125^2 + 17544^2 .

It is a cyclic number.

It is not a de Polignac number, because 990307561 - 2¹ = 990307559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (990307541) 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, 6782856 + ... + 6783001.

It is an arithmetic number, because the mean of its divisors is an integer number (250968373).

Almost surely, 2^990307561 is an apocalyptic number.

It is an amenable number.

990307561 is a deficient number, since it is larger than the sum of its proper divisors (13565931).

990307561 is a wasteful number, since it uses less digits than its factorization.

990307561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13565930.

The product of its (nonzero) digits is 51030, while the sum is 40.

The square root of 990307561 is about 31469.1525306927. The cubic root of 990307561 is about 996.7586922754.

The spelling of 990307561 in words is "nine hundred ninety million, three hundred seven thousand, five hundred sixty-one".