1621009 has 4 divisors (see below), whose sum is σ = 1745716. Its totient is φ = 1496304.

The previous prime is 1620989. The next prime is 1621019. The reversal of 1621009 is 9001261.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 9001261 = 151 ⋅59611.

It can be written as a sum of positive squares in 2 ways, for example, as 291600 + 1329409 = 540^2 + 1153^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621009 - 2⁵ = 1620977 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1621019) 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, 62334 + ... + 62359.

It is an arithmetic number, because the mean of its divisors is an integer number (436429).

2^1621009 is an apocalyptic number.

It is an amenable number.

1621009 is a deficient number, since it is larger than the sum of its proper divisors (124707).

1621009 is a wasteful number, since it uses less digits than its factorization.

1621009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 124706.

The product of its (nonzero) digits is 108, while the sum is 19.

The square root of 1621009 is about 1273.1885170704. The cubic root of 1621009 is about 117.4704075168.

It can be divided in two parts, 16 and 21009, that added together give a square (21025 = 145²).

The spelling of 1621009 in words is "one million, six hundred twenty-one thousand, nine".