19810421 has 12 divisors (see below), whose sum is σ = 20860644. Its totient is φ = 18796800.

The previous prime is 19810411. The next prime is 19810447. The reversal of 19810421 is 12401891.

It can be written as a sum of positive squares in 6 ways, for example, as 12460900 + 7349521 = 3530^2 + 2711^2 .

It is a de Polignac number, because none of the positive numbers 2^k-19810421 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 (19810411) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 222545 + ... + 222633.

It is an arithmetic number, because the mean of its divisors is an integer number (1738387).

Almost surely, 2^19810421 is an apocalyptic number.

It is an amenable number.

19810421 is a deficient number, since it is larger than the sum of its proper divisors (1050223).

19810421 is an frugal number, since it uses more digits than its factorization.

19810421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280 (or 191 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 26.

The square root of 19810421 is about 4450.8899110178. The cubic root of 19810421 is about 270.5813764274.

The spelling of 19810421 in words is "nineteen million, eight hundred ten thousand, four hundred twenty-one".