1561901 has 4 divisors (see below), whose sum is σ = 1703904. Its totient is φ = 1419900.

The previous prime is 1561891. The next prime is 1561919. The reversal of 1561901 is 1091651.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1091651 = 11 ⋅99241.

It is a cyclic number.

It is not a de Polignac number, because 1561901 - 2¹⁰ = 1560877 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a nialpdrome in base 11.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561601) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 70985 + ... + 71006.

It is an arithmetic number, because the mean of its divisors is an integer number (425976).

2^1561901 is an apocalyptic number.

1561901 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1561901 is a deficient number, since it is larger than the sum of its proper divisors (142003).

1561901 is a wasteful number, since it uses less digits than its factorization.

1561901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 142002.

The product of its (nonzero) digits is 270, while the sum is 23.

The square root of 1561901 is about 1249.7603770323. The cubic root of 1561901 is about 116.0248906159.

It can be divided in two parts, 15 and 61901, that added together give a palindrome (61916).

The spelling of 1561901 in words is "one million, five hundred sixty-one thousand, nine hundred one".