15561998 has 4 divisors (see below), whose sum is σ = 23343000. Its totient is φ = 7780998.

The previous prime is 15561991. The next prime is 15562013. The reversal of 15561998 is 89916551.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15561991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 3890498 + ... + 3890501.

It is an arithmetic number, because the mean of its divisors is an integer number (5835750).

Almost surely, 2^15561998 is an apocalyptic number.

15561998 is a deficient number, since it is larger than the sum of its proper divisors (7781002).

15561998 is an equidigital number, since it uses as much as digits as its factorization.

15561998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7781001.

The product of its digits is 97200, while the sum is 44.

The square root of 15561998 is about 3944.8698330870. The cubic root of 15561998 is about 249.6635367063.

The spelling of 15561998 in words is "fifteen million, five hundred sixty-one thousand, nine hundred ninety-eight".