21505246201 has 4 divisors (see below), whose sum is σ = 21507133072. Its totient is φ = 21503359332.

The previous prime is 21505246187. The next prime is 21505246207. The reversal of 21505246201 is 10264250512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21505246201 - 2¹³ = 21505238009 is a prime.

It is a super-2 number, since 2×21505246201² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21505246201.

It is not an unprimeable number, because it can be changed into a prime (21505246207) 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, 926235 + ... + 949168.

It is an arithmetic number, because the mean of its divisors is an integer number (5376783268).

Almost surely, 2^21505246201 is an apocalyptic number.

It is an amenable number.

21505246201 is a deficient number, since it is larger than the sum of its proper divisors (1886871).

21505246201 is a wasteful number, since it uses less digits than its factorization.

21505246201 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1886870.

The product of its (nonzero) digits is 4800, while the sum is 28.

Adding to 21505246201 its reverse (10264250512), we get a palindrome (31769496713).

The spelling of 21505246201 in words is "twenty-one billion, five hundred five million, two hundred forty-six thousand, two hundred one".