21390817536 has 243 divisors, whose sum is σ = 68037147633. Its totient is φ = 6458664960.

The previous prime is 21390817523. The next prime is 21390817549. The reversal of 21390817536 is 63571809312.

The square root of 21390817536 is 146256.

It is a perfect power (a square), and thus also a powerful number.

21390817536 is a `hidden beast` number, since 2 + 1 + 39 + 0 + 81 + 7 + 536 = 666.

It is an interprime number because it is at equal distance from previous prime (21390817523) and next prime (21390817549).

It can be written as a sum of positive squares in only one way, i.e., 3686918400 + 17703899136 = 60720^2 + 133056^2 .

It is a super-2 number, since 2×21390817536² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21390817491 and 21390817500.

It is an unprimeable number.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 77223030 + ... + 77223306.

Almost surely, 2^21390817536 is an apocalyptic number.

21390817536 is the 146256-th square number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21390817536

21390817536 is an abundant number, since it is smaller than the sum of its proper divisors (46646330097).

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

21390817536 is an equidigital number, since it uses as much as digits as its factorization.

21390817536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 598 (or 293 counting only the distinct ones).

The product of its (nonzero) digits is 272160, while the sum is 45.

The spelling of 21390817536 in words is "twenty-one billion, three hundred ninety million, eight hundred seventeen thousand, five hundred thirty-six".