21465840 has 160 divisors (see below), whose sum is σ = 74566656. Its totient is φ = 5063680.

The previous prime is 21465827. The next prime is 21465841. The reversal of 21465840 is 4856412.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 21465798 and 21465807.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21465841) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 123994 + ... + 124166.

Almost surely, 2^21465840 is an apocalyptic number.

21465840 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 21465840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37283328).

21465840 is an abundant number, since it is smaller than the sum of its proper divisors (53100816).

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

21465840 is a wasteful number, since it uses less digits than its factorization.

21465840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 241 counting only the distinct ones).

The product of its (nonzero) digits is 7680, while the sum is 30.

The square root of 21465840 is about 4633.1242159044. The cubic root of 21465840 is about 277.9175436492.

The spelling of 21465840 in words is "twenty-one million, four hundred sixty-five thousand, eight hundred forty".