21257420 has 12 divisors (see below), whose sum is σ = 44640624. Its totient is φ = 8502960.

The previous prime is 21257419. The next prime is 21257461. The reversal of 21257420 is 2475212.

It is a happy number.

It is a plaindrome in base 16.

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 3 ways as a sum of consecutive naturals, for example, 531416 + ... + 531455.

It is an arithmetic number, because the mean of its divisors is an integer number (3720052).

Almost surely, 2^21257420 is an apocalyptic number.

21257420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21257420 is an abundant number, since it is smaller than the sum of its proper divisors (23383204).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21257420 is a wasteful number, since it uses less digits than its factorization.

21257420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1062880 (or 1062878 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 23.

The square root of 21257420 is about 4610.5769704019. The cubic root of 21257420 is about 277.0151477248.

The spelling of 21257420 in words is "twenty-one million, two hundred fifty-seven thousand, four hundred twenty".