21265240 has 16 divisors (see below), whose sum is σ = 47846880. Its totient is φ = 8506080.

The previous prime is 21265219. The next prime is 21265241. The reversal of 21265240 is 4256212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21265241) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 265776 + ... + 265855.

It is an arithmetic number, because the mean of its divisors is an integer number (2990430).

Almost surely, 2^21265240 is an apocalyptic number.

21265240 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21265240 is an abundant number, since it is smaller than the sum of its proper divisors (26581640).

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

21265240 is a wasteful number, since it uses less digits than its factorization.

21265240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 531642 (or 531638 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 22.

The square root of 21265240 is about 4611.4249424663. The cubic root of 21265240 is about 277.0491122240.

Subtracting from 21265240 its reverse (4256212), we obtain a triangular number (17009028 = T₅₈₃₂).

The spelling of 21265240 in words is "twenty-one million, two hundred sixty-five thousand, two hundred forty".