21264021601 has 4 divisors (see below), whose sum is σ = 21266212500. Its totient is φ = 21261830704.

The previous prime is 21264021557. The next prime is 21264021629. The reversal of 21264021601 is 10612046212.

It is a happy number.

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 1490037201 + 19773984400 = 38601^2 + 140620^2 .

It is a cyclic number.

It is not a de Polignac number, because 21264021601 - 2⁷ = 21264021473 is a prime.

It is a super-2 number, since 2×21264021601² (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 (21264021631) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1080826 + ... + 1100323.

It is an arithmetic number, because the mean of its divisors is an integer number (5316553125).

Almost surely, 2^21264021601 is an apocalyptic number.

It is an amenable number.

21264021601 is a deficient number, since it is larger than the sum of its proper divisors (2190899).

21264021601 is an equidigital number, since it uses as much as digits as its factorization.

21264021601 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2190898.

The product of its (nonzero) digits is 1152, while the sum is 25.

Adding to 21264021601 its reverse (10612046212), we get a palindrome (31876067813).

The spelling of 21264021601 in words is "twenty-one billion, two hundred sixty-four million, twenty-one thousand, six hundred one".