1621909 has 2 divisors, whose sum is σ = 1621910. Its totient is φ = 1621908.

The previous prime is 1621877. The next prime is 1621931. The reversal of 1621909 is 9091261.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1368900 + 253009 = 1170^2 + 503^2 .

It is a cyclic number.

It is not a de Polignac number, because 1621909 - 2⁵ = 1621877 is a prime.

1621909 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1621979) 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 as a sum of consecutive naturals, namely, 810954 + 810955.

It is an arithmetic number, because the mean of its divisors is an integer number (810955).

2^1621909 is an apocalyptic number.

It is an amenable number.

1621909 is a deficient number, since it is larger than the sum of its proper divisors (1).

1621909 is an equidigital number, since it uses as much as digits as its factorization.

1621909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 972, while the sum is 28.

The square root of 1621909 is about 1273.5419113637. The cubic root of 1621909 is about 117.4921437331.

The spelling of 1621909 in words is "one million, six hundred twenty-one thousand, nine hundred nine".