19801421 has 2 divisors, whose sum is σ = 19801422. Its totient is φ = 19801420.

The previous prime is 19801409. The next prime is 19801423. The reversal of 19801421 is 12410891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18966025 + 835396 = 4355^2 + 914^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-19801421 is a prime.

Together with 19801423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (19801423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9900710 + 9900711.

It is an arithmetic number, because the mean of its divisors is an integer number (9900711).

Almost surely, 2^19801421 is an apocalyptic number.

It is an amenable number.

19801421 is a deficient number, since it is larger than the sum of its proper divisors (1).

19801421 is an equidigital number, since it uses as much as digits as its factorization.

19801421 is an evil number, because the sum of its binary digits is even.

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

The square root of 19801421 is about 4449.8787623934. The cubic root of 19801421 is about 270.5403946084.

The spelling of 19801421 in words is "nineteen million, eight hundred one thousand, four hundred twenty-one".