21256413552 has 240 divisors, whose sum is σ = 70253717760. Its totient is φ = 6101827200.

The previous prime is 21256413509. The next prime is 21256413587. The reversal of 21256413552 is 25531465212.

21256413552 is a `hidden beast` number, since 2 + 1 + 2 + 5 + 641 + 3 + 5 + 5 + 2 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1709277 + ... + 1721667.

It is an arithmetic number, because the mean of its divisors is an integer number (292723824).

Almost surely, 2^21256413552 is an apocalyptic number.

21256413552 is a gapful number since it is divisible by the number (22) 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 21256413552, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35126858880).

21256413552 is an abundant number, since it is smaller than the sum of its proper divisors (48997304208).

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

21256413552 is a wasteful number, since it uses less digits than its factorization.

21256413552 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12457 (or 12426 counting only the distinct ones).

The product of its digits is 72000, while the sum is 36.

Adding to 21256413552 its reverse (25531465212), we get a palindrome (46787878764).

The spelling of 21256413552 in words is "twenty-one billion, two hundred fifty-six million, four hundred thirteen thousand, five hundred fifty-two".