1561621 has 4 divisors (see below), whose sum is σ = 1615500. Its totient is φ = 1507744.

The previous prime is 1561607. The next prime is 1561633. The reversal of 1561621 is 1261651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1261651 = 797 ⋅1583.

It can be written as a sum of positive squares in 2 ways, for example, as 1322500 + 239121 = 1150^2 + 489^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561621 - 2⁵ = 1561589 is a prime.

It is a Duffinian number.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 1561592 and 1561601.

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 (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26896 + ... + 26953.

It is an arithmetic number, because the mean of its divisors is an integer number (403875).

2^1561621 is an apocalyptic number.

It is an amenable number.

1561621 is a deficient number, since it is larger than the sum of its proper divisors (53879).

1561621 is an equidigital number, since it uses as much as digits as its factorization.

1561621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 53878.

The product of its digits is 360, while the sum is 22.

The square root of 1561621 is about 1249.6483505371. The cubic root of 1561621 is about 116.0179569902.

The spelling of 1561621 in words is "one million, five hundred sixty-one thousand, six hundred twenty-one".