21001215003540 has 48 divisors (see below), whose sum is σ = 58803601231872. Its totient is φ = 5600305027456.

The previous prime is 21001215003451. The next prime is 21001215003541. The reversal of 21001215003540 is 4530051210012.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 21001215003540.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001215003541) 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, 32907562 + ... + 33539678.

It is an arithmetic number, because the mean of its divisors is an integer number (1225075025664).

Almost surely, 2^{21001215003540} is an apocalyptic number.

21001215003540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001215003540 is an abundant number, since it is smaller than the sum of its proper divisors (37802386228332).

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

21001215003540 is a wasteful number, since it uses less digits than its factorization.

21001215003540 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1185856 (or 1185854 counting only the distinct ones).

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21001215003540 its reverse (4530051210012), we get a palindrome (25531266213552).

The spelling of 21001215003540 in words is "twenty-one trillion, one billion, two hundred fifteen million, three thousand, five hundred forty".