21125225021 has 4 divisors (see below), whose sum is σ = 21131353500. Its totient is φ = 21119096544.

The previous prime is 21125224997. The next prime is 21125225041. The reversal of 21125225021 is 12052252112.

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 777628996 + 20347596025 = 27886^2 + 142645^2 .

It is a cyclic number.

It is not a de Polignac number, because 21125225021 - 2²² = 21121030717 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21125225041) 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, 3059066 + ... + 3065963.

It is an arithmetic number, because the mean of its divisors is an integer number (5282838375).

Almost surely, 2^21125225021 is an apocalyptic number.

It is an amenable number.

21125225021 is a deficient number, since it is larger than the sum of its proper divisors (6128479).

21125225021 is an equidigital number, since it uses as much as digits as its factorization.

21125225021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6128478.

The product of its (nonzero) digits is 800, while the sum is 23.

Adding to 21125225021 its reverse (12052252112), we get a palindrome (33177477133).

The spelling of 21125225021 in words is "twenty-one billion, one hundred twenty-five million, two hundred twenty-five thousand, twenty-one".