21457925 has 6 divisors (see below), whose sum is σ = 26607858. Its totient is φ = 17166320.

The previous prime is 21457871. The next prime is 21457939. The reversal of 21457925 is 52975412.

It can be written as a sum of positive squares in 3 ways, for example, as 7086244 + 14371681 = 2662^2 + 3791^2 .

It is not a de Polignac number, because 21457925 - 2¹⁰ = 21456901 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 429134 + ... + 429183.

It is an arithmetic number, because the mean of its divisors is an integer number (4434643).

Almost surely, 2^21457925 is an apocalyptic number.

21457925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21457925 is a deficient number, since it is larger than the sum of its proper divisors (5149933).

21457925 is an equidigital number, since it uses as much as digits as its factorization.

21457925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 858327 (or 858322 counting only the distinct ones).

The product of its digits is 25200, while the sum is 35.

The square root of 21457925 is about 4632.2699619085. The cubic root of 21457925 is about 277.8833810327.

The spelling of 21457925 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred twenty-five".