1921820401 has 6 divisors (see below), whose sum is σ = 1990376102. Its totient is φ = 1855549920.

The previous prime is 1921820399. The next prime is 1921820423. The reversal of 1921820401 is 1040281291.

It can be written as a sum of positive squares in 3 ways, for example, as 460746225 + 1461074176 = 21465^2 + 38224^2 .

It is not a de Polignac number, because 1921820401 - 2¹ = 1921820399 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1921820401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1921830401) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1141740 + ... + 1143421.

Almost surely, 2^1921820401 is an apocalyptic number.

It is an amenable number.

1921820401 is a deficient number, since it is larger than the sum of its proper divisors (68555701).

1921820401 is an equidigital number, since it uses as much as digits as its factorization.

1921820401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2285219 (or 2285190 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 28.

The square root of 1921820401 is about 43838.5720684422. The cubic root of 1921820401 is about 1243.2856844954.

The spelling of 1921820401 in words is "one billion, nine hundred twenty-one million, eight hundred twenty thousand, four hundred one".