21025540 has 12 divisors (see below), whose sum is σ = 44153676. Its totient is φ = 8410208.

The previous prime is 21025513. The next prime is 21025561. The reversal of 21025540 is 4552012.

It can be written as a sum of positive squares in 2 ways, for example, as 15178816 + 5846724 = 3896^2 + 2418^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 525619 + ... + 525658.

It is an arithmetic number, because the mean of its divisors is an integer number (3679473).

Almost surely, 2^21025540 is an apocalyptic number.

21025540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21025540 is an abundant number, since it is smaller than the sum of its proper divisors (23128136).

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

21025540 is a wasteful number, since it uses less digits than its factorization.

21025540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1051286 (or 1051284 counting only the distinct ones).

The product of its (nonzero) digits is 400, while the sum is 19.

The square root of 21025540 is about 4585.3614906570. The cubic root of 21025540 is about 276.0042182370.

Adding to 21025540 its reverse (4552012), we get a palindrome (25577552).

The spelling of 21025540 in words is "twenty-one million, twenty-five thousand, five hundred forty".