21253423261 has 4 divisors (see below), whose sum is σ = 24289626592. Its totient is φ = 18217219932.

The previous prime is 21253423253. The next prime is 21253423271. The reversal of 21253423261 is 16232435212.

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 21253423261 - 2³ = 21253423253 is a prime.

It is a super-2 number, since 2×21253423261² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21253423201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1518101655 + ... + 1518101668.

It is an arithmetic number, because the mean of its divisors is an integer number (6072406648).

Almost surely, 2^21253423261 is an apocalyptic number.

It is an amenable number.

21253423261 is a deficient number, since it is larger than the sum of its proper divisors (3036203331).

21253423261 is an equidigital number, since it uses as much as digits as its factorization.

21253423261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3036203330.

The product of its digits is 17280, while the sum is 31.

Adding to 21253423261 its reverse (16232435212), we get a palindrome (37485858473).

The spelling of 21253423261 in words is "twenty-one billion, two hundred fifty-three million, four hundred twenty-three thousand, two hundred sixty-one".