21801001 has 2 divisors, whose sum is σ = 21801002. Its totient is φ = 21801000.

The previous prime is 21800963. The next prime is 21801019. The reversal of 21801001 is 10010812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13104400 + 8696601 = 3620^2 + 2949^2 .

It is a cyclic number.

It is not a de Polignac number, because 21801001 - 2⁷ = 21800873 is a prime.

It is not a weakly prime, because it can be changed into another prime (21801061) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10900500 + 10900501.

It is an arithmetic number, because the mean of its divisors is an integer number (10900501).

Almost surely, 2^21801001 is an apocalyptic number.

It is an amenable number.

21801001 is a deficient number, since it is larger than the sum of its proper divisors (1).

21801001 is an equidigital number, since it uses as much as digits as its factorization.

21801001 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 13.

The square root of 21801001 is about 4669.1542060634. The cubic root of 21801001 is about 279.3565197718.

Adding to 21801001 its reverse (10010812), we get a palindrome (31811813).

The spelling of 21801001 in words is "twenty-one million, eight hundred one thousand, one".