21261420 has 48 divisors (see below), whose sum is σ = 66148320. Its totient is φ = 5669568.

The previous prime is 21261413. The next prime is 21261433. The reversal of 21261420 is 2416212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 21261393 and 21261402.

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 15 ways as a sum of consecutive naturals, for example, 19147 + ... + 20226.

It is an arithmetic number, because the mean of its divisors is an integer number (1378090).

Almost surely, 2^21261420 is an apocalyptic number.

21261420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21261420 is an abundant number, since it is smaller than the sum of its proper divisors (44886900).

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

21261420 is a wasteful number, since it uses less digits than its factorization.

21261420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39391 (or 39383 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 18.

The square root of 21261420 is about 4611.0107351859. The cubic root of 21261420 is about 277.0325219106.

Adding to 21261420 its reverse (2416212), we get a palindrome (23677632).

The spelling of 21261420 in words is "twenty-one million, two hundred sixty-one thousand, four hundred twenty".