21273840 has 300 divisors, whose sum is σ = 87233256. Its totient is φ = 4790016.

The previous prime is 21273839. The next prime is 21273841. The reversal of 21273840 is 4837212.

It is an interprime number because it is at equal distance from previous prime (21273839) and next prime (21273841).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21273841) by changing a digit.

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 59 ways as a sum of consecutive naturals, for example, 317487 + ... + 317553.

Almost surely, 2^21273840 is an apocalyptic number.

21273840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21273840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (43616628).

21273840 is an abundant number, since it is smaller than the sum of its proper divisors (65959416).

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

21273840 is a wasteful number, since it uses less digits than its factorization.

21273840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 106 (or 84 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21273840 is about 4612.3573148662. The cubic root of 21273840 is about 277.0864548740.

The spelling of 21273840 in words is "twenty-one million, two hundred seventy-three thousand, eight hundred forty".