25121821 has 4 divisors (see below), whose sum is σ = 25344252. Its totient is φ = 24899392.

The previous prime is 25121809. The next prime is 25121867. The reversal of 25121821 is 12812152.

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 1792921 + 23328900 = 1339^2 + 4830^2 .

It is a cyclic number.

It is not a de Polignac number, because 25121821 - 2¹³ = 25113629 is a prime.

It is a super-2 number, since 2×25121821² = 1262211780712082, which contains 22 as substring.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 25121792 and 25121801.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25121881) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 111046 + ... + 111271.

It is an arithmetic number, because the mean of its divisors is an integer number (6336063).

Almost surely, 2^25121821 is an apocalyptic number.

It is an amenable number.

25121821 is a deficient number, since it is larger than the sum of its proper divisors (222431).

25121821 is a wasteful number, since it uses less digits than its factorization.

25121821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 222430.

The product of its digits is 320, while the sum is 22.

The square root of 25121821 is about 5012.1672956916. The cubic root of 25121821 is about 292.8759468167.

Adding to 25121821 its reverse (12812152), we get a palindrome (37933973).

The spelling of 25121821 in words is "twenty-five million, one hundred twenty-one thousand, eight hundred twenty-one".