1621901 has 4 divisors (see below), whose sum is σ = 1630332. Its totient is φ = 1613472.

The previous prime is 1621877. The next prime is 1621909. The reversal of 1621901 is 1091261.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1060900 + 561001 = 1030^2 + 749^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1621901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621909) 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, 3920 + ... + 4313.

It is an arithmetic number, because the mean of its divisors is an integer number (407583).

2^1621901 is an apocalyptic number.

It is an amenable number.

1621901 is a deficient number, since it is larger than the sum of its proper divisors (8431).

1621901 is an equidigital number, since it uses as much as digits as its factorization.

1621901 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8430.

The product of its (nonzero) digits is 108, while the sum is 20.

The square root of 1621901 is about 1273.5387705131. The cubic root of 1621901 is about 117.4919505577.

The spelling of 1621901 in words is "one million, six hundred twenty-one thousand, nine hundred one".