21147840 has 168 divisors, whose sum is σ = 83210400. Its totient is φ = 4829184.

The previous prime is 21147839. The next prime is 21147851. The reversal of 21147840 is 4874112.

It is a tau number, because it is divible by the number of its divisors (168).

It is a super-2 number, since 2×21147840² = 894462273331200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19636 + ... + 20684.

It is an arithmetic number, because the mean of its divisors is an integer number (495300).

Almost surely, 2^21147840 is an apocalyptic number.

21147840 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 21147840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (41605200).

21147840 is an abundant number, since it is smaller than the sum of its proper divisors (62062560).

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

21147840 is a wasteful number, since it uses less digits than its factorization.

21147840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1079 (or 1066 counting only the distinct ones).

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

The square root of 21147840 is about 4598.6780709243. The cubic root of 21147840 is about 276.5383317959.

The spelling of 21147840 in words is "twenty-one million, one hundred forty-seven thousand, eight hundred forty".