21256045532540 has 192 divisors, whose sum is σ = 56312482238208. Its totient is φ = 6563071549440.

The previous prime is 21256045532509. The next prime is 21256045532591. The reversal of 21256045532540 is 4523554065212.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21256045532491 and 21256045532500.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 125351492 + ... + 125520948.

It is an arithmetic number, because the mean of its divisors is an integer number (293294178324).

Almost surely, 2^{21256045532540} is an apocalyptic number.

21256045532540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21256045532540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28156241119104).

21256045532540 is an abundant number, since it is smaller than the sum of its proper divisors (35056436705668).

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

21256045532540 is a wasteful number, since it uses less digits than its factorization.

21256045532540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 169609 (or 169525 counting only the distinct ones).

The product of its (nonzero) digits is 1440000, while the sum is 44.

Adding to 21256045532540 its reverse (4523554065212), we get a palindrome (25779599597752).

The spelling of 21256045532540 in words is "twenty-one trillion, two hundred fifty-six billion, forty-five million, five hundred thirty-two thousand, five hundred forty".