21420001 has 2 divisors, whose sum is σ = 21420002. Its totient is φ = 21420000.

The previous prime is 21419939. The next prime is 21420013. The reversal of 21420001 is 10002412.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20566225 + 853776 = 4535^2 + 924^2 .

It is a cyclic number.

It is not a de Polignac number, because 21420001 - 2¹¹ = 21417953 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21420001.

It is not a weakly prime, because it can be changed into another prime (21420031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10710000 + 10710001.

It is an arithmetic number, because the mean of its divisors is an integer number (10710001).

Almost surely, 2^21420001 is an apocalyptic number.

It is an amenable number.

21420001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21420001 is an equidigital number, since it uses as much as digits as its factorization.

21420001 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21420001 is about 4628.1746941964. The cubic root of 21420001 is about 277.7195773118.

Adding to 21420001 its reverse (10002412), we get a palindrome (31422413).

The spelling of 21420001 in words is "twenty-one million, four hundred twenty thousand, one".