25000000021 has 2 divisors, whose sum is σ = 25000000022. Its totient is φ = 25000000020.

The previous prime is 25000000013. The next prime is 25000000111. The reversal of 25000000021 is 12000000052.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12947253796 + 12052746225 = 113786^2 + 109785^2 .

It is a cyclic number.

It is not a de Polignac number, because 25000000021 - 2³ = 25000000013 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 24999999944 and 25000000007.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25000000621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12500000010 + 12500000011.

It is an arithmetic number, because the mean of its divisors is an integer number (12500000011).

Almost surely, 2^25000000021 is an apocalyptic number.

It is an amenable number.

25000000021 is a deficient number, since it is larger than the sum of its proper divisors (1).

25000000021 is an equidigital number, since it uses as much as digits as its factorization.

25000000021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 20, while the sum is 10.

Adding to 25000000021 its reverse (12000000052), we get a palindrome (37000000073).

The spelling of 25000000021 in words is "twenty-five billion, twenty-one", and thus it is an aban number and an uban number.