1631561 has 4 divisors (see below), whose sum is σ = 1684224. Its totient is φ = 1578900.

The previous prime is 1631557. The next prime is 1631573. The reversal of 1631561 is 1651361.

It is a happy number.

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.

It is a cyclic number.

It is not a de Polignac number, because 1631561 - 2² = 1631557 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1631521) 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, 26285 + ... + 26346.

It is an arithmetic number, because the mean of its divisors is an integer number (421056).

2^1631561 is an apocalyptic number.

It is an amenable number.

1631561 is a deficient number, since it is larger than the sum of its proper divisors (52663).

1631561 is an equidigital number, since it uses as much as digits as its factorization.

1631561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52662.

The product of its digits is 540, while the sum is 23.

The square root of 1631561 is about 1277.3257219676. The cubic root of 1631561 is about 117.7247486509.

The spelling of 1631561 in words is "one million, six hundred thirty-one thousand, five hundred sixty-one".