21478140 has 72 divisors (see below), whose sum is σ = 68992560. Its totient is φ = 5389824.

The previous prime is 21478117. The next prime is 21478147. The reversal of 21478140 is 4187412.

It is a super-2 number, since 2×21478140² = 922620995719200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21478147) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 450 + ... + 6569.

It is an arithmetic number, because the mean of its divisors is an integer number (958230).

Almost surely, 2^21478140 is an apocalyptic number.

21478140 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 21478140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34496280).

21478140 is an abundant number, since it is smaller than the sum of its proper divisors (47514420).

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

21478140 is a wasteful number, since it uses less digits than its factorization.

21478140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7051 (or 7046 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 27.

The square root of 21478140 is about 4634.4514238473. The cubic root of 21478140 is about 277.9706160824.

The spelling of 21478140 in words is "twenty-one million, four hundred seventy-eight thousand, one hundred forty".