25215821 has 2 divisors, whose sum is σ = 25215822. Its totient is φ = 25215820.

The previous prime is 25215781. The next prime is 25215823. The reversal of 25215821 is 12851252.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 25140196 + 75625 = 5014^2 + 275^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25215821 is a prime.

Together with 25215823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25215823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12607910 + 12607911.

It is an arithmetic number, because the mean of its divisors is an integer number (12607911).

Almost surely, 2^25215821 is an apocalyptic number.

It is an amenable number.

25215821 is a deficient number, since it is larger than the sum of its proper divisors (1).

25215821 is an equidigital number, since it uses as much as digits as its factorization.

25215821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1600, while the sum is 26.

The square root of 25215821 is about 5021.5357212709. The cubic root of 25215821 is about 293.2407833312.

The spelling of 25215821 in words is "twenty-five million, two hundred fifteen thousand, eight hundred twenty-one".