21465440 has 96 divisors (see below), whose sum is σ = 55883520. Its totient is φ = 7755264.

The previous prime is 21465397. The next prime is 21465443. The reversal of 21465440 is 4456412.

It is a super-2 number, since 2×21465440² = 921530228787200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21465443) 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, 69767 + ... + 70073.

It is an arithmetic number, because the mean of its divisors is an integer number (582120).

Almost surely, 2^21465440 is an apocalyptic number.

21465440 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 21465440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27941760).

21465440 is an abundant number, since it is smaller than the sum of its proper divisors (34418080).

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

21465440 is a wasteful number, since it uses less digits than its factorization.

21465440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364 (or 356 counting only the distinct ones).

The product of its (nonzero) digits is 3840, while the sum is 26.

The square root of 21465440 is about 4633.0810482874. The cubic root of 21465440 is about 277.9158173761.

Subtracting from 21465440 its reverse (4456412), we obtain a triangular number (17009028 = T₅₈₃₂).

The spelling of 21465440 in words is "twenty-one million, four hundred sixty-five thousand, four hundred forty".