21508400201 has 4 divisors (see below), whose sum is σ = 21550656900. Its totient is φ = 21466143504.

The previous prime is 21508400189. The next prime is 21508400203. The reversal of 21508400201 is 10200480512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 7424407225 + 14083992976 = 86165^2 + 118676^2 .

It is a cyclic number.

It is not a de Polignac number, because 21508400201 - 2¹⁰ = 21508399177 is a prime.

It is a super-2 number, since 2×21508400201² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21508400203) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21127586 + ... + 21128603.

It is an arithmetic number, because the mean of its divisors is an integer number (5387664225).

Almost surely, 2^21508400201 is an apocalyptic number.

It is an amenable number.

21508400201 is a deficient number, since it is larger than the sum of its proper divisors (42256699).

21508400201 is an equidigital number, since it uses as much as digits as its factorization.

21508400201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42256698.

The product of its (nonzero) digits is 640, while the sum is 23.

Adding to 21508400201 its reverse (10200480512), we get a palindrome (31708880713).

The spelling of 21508400201 in words is "twenty-one billion, five hundred eight million, four hundred thousand, two hundred one".