1561999 has 8 divisors (see below), whose sum is σ = 1647072. Its totient is φ = 1478400.

The previous prime is 1561919. The next prime is 1562051. The reversal of 1561999 is 9991651.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1561999 - 2¹³ = 1553807 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561919) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2299 + ... + 2899.

It is an arithmetic number, because the mean of its divisors is an integer number (205884).

2^1561999 is an apocalyptic number.

1561999 is a deficient number, since it is larger than the sum of its proper divisors (85073).

1561999 is a wasteful number, since it uses less digits than its factorization.

1561999 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 737.

The product of its digits is 21870, while the sum is 40.

The square root of 1561999 is about 1249.7995839334. The cubic root of 1561999 is about 116.0273171892.

The spelling of 1561999 in words is "one million, five hundred sixty-one thousand, nine hundred ninety-nine".