998072561 has 4 divisors (see below), whose sum is σ = 1007229300. Its totient is φ = 988915824.

The previous prime is 998072539. The next prime is 998072573. The reversal of 998072561 is 165270899.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165270899 = 61 ⋅2709359.

It can be written as a sum of positive squares in 2 ways, for example, as 669774400 + 328298161 = 25880^2 + 18119^2 .

It is a cyclic number.

It is not a de Polignac number, because 998072561 - 2¹⁴ = 998056177 is a prime.

It is a super-2 number, since 2×998072561² = 1992297674042197442, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (998072531) 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, 4578206 + ... + 4578423.

It is an arithmetic number, because the mean of its divisors is an integer number (251807325).

Almost surely, 2^998072561 is an apocalyptic number.

998072561 is the 14129-th centered decagonal number.

It is an amenable number.

998072561 is a deficient number, since it is larger than the sum of its proper divisors (9156739).

998072561 is a wasteful number, since it uses less digits than its factorization.

998072561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9156738.

The product of its (nonzero) digits is 272160, while the sum is 47.

The square root of 998072561 is about 31592.2864161491. The cubic root of 998072561 is about 999.3571071106.

The spelling of 998072561 in words is "nine hundred ninety-eight million, seventy-two thousand, five hundred sixty-one".