21036540 has 48 divisors (see below), whose sum is σ = 67318272. Its totient is φ = 4808256.

The previous prime is 21036539. The next prime is 21036563. The reversal of 21036540 is 4563012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24624 + ... + 25463.

It is an arithmetic number, because the mean of its divisors is an integer number (1402464).

Almost surely, 2^21036540 is an apocalyptic number.

21036540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21036540 is an abundant number, since it is smaller than the sum of its proper divisors (46281732).

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

21036540 is a wasteful number, since it uses less digits than its factorization.

21036540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50106 (or 50104 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21036540 is about 4586.5608030419. The cubic root of 21036540 is about 276.0523425197.

Adding to 21036540 its reverse (4563012), we get a palindrome (25599552).

The spelling of 21036540 in words is "twenty-one million, thirty-six thousand, five hundred forty".