21578140 has 48 divisors (see below), whose sum is σ = 48121920. Its totient is φ = 8110080.

The previous prime is 21578093. The next prime is 21578147. The reversal of 21578140 is 4187512.

It is a super-2 number, since 2×21578140² = 931232251719200, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21578099 and 21578108.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21578147) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27676 + ... + 28444.

It is an arithmetic number, because the mean of its divisors is an integer number (1002540).

Almost surely, 2^21578140 is an apocalyptic number.

21578140 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 21578140, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24060960).

21578140 is an abundant number, since it is smaller than the sum of its proper divisors (26543780).

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

21578140 is a wasteful number, since it uses less digits than its factorization.

21578140 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 862 (or 860 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 21578140 is about 4645.2276585761. The cubic root of 21578140 is about 278.4013491094.

The spelling of 21578140 in words is "twenty-one million, five hundred seventy-eight thousand, one hundred forty".