21126540 has 24 divisors (see below), whose sum is σ = 59154480. Its totient is φ = 5633728.

The previous prime is 21126533. The next prime is 21126551. The reversal of 21126540 is 4562112.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 175995 + ... + 176114.

It is an arithmetic number, because the mean of its divisors is an integer number (2464770).

Almost surely, 2^21126540 is an apocalyptic number.

21126540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21126540 is an abundant number, since it is smaller than the sum of its proper divisors (38027940).

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

21126540 is a wasteful number, since it uses less digits than its factorization.

21126540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 352121 (or 352119 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21126540 is about 4596.3616045738. The cubic root of 21126540 is about 276.4454579276.

Adding to 21126540 its reverse (4562112), we get a palindrome (25688652).

The spelling of 21126540 in words is "twenty-one million, one hundred twenty-six thousand, five hundred forty".