21647139840 has 528 divisors, whose sum is σ = 78969526272. Its totient is φ = 5685313536.

The previous prime is 21647139827. The next prime is 21647139847. The reversal of 21647139840 is 4893174612.

21647139840 is a `hidden beast` number, since 216 + 4 + 7 + 1 + 398 + 40 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21647139847) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 158008252 + ... + 158008388.

Almost surely, 2^21647139840 is an apocalyptic number.

21647139840 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 21647139840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39484763136).

21647139840 is an abundant number, since it is smaller than the sum of its proper divisors (57322386432).

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

21647139840 is a wasteful number, since it uses less digits than its factorization.

21647139840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The spelling of 21647139840 in words is "twenty-one billion, six hundred forty-seven million, one hundred thirty-nine thousand, eight hundred forty".