21897872640 has 864 divisors, whose sum is σ = 92218412160. Its totient is φ = 4904976384.

The previous prime is 21897872629. The next prime is 21897872641. The reversal of 21897872640 is 4627879812.

It is a happy number.

21897872640 is a `hidden beast` number, since 218 + 97 + 87 + 264 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21897872641) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 113460384 + ... + 113460576.

Almost surely, 2^21897872640 is an apocalyptic number.

21897872640 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 21897872640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46109206080).

21897872640 is an abundant number, since it is smaller than the sum of its proper divisors (70320539520).

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

21897872640 is a wasteful number, since it uses less digits than its factorization.

21897872640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 304 (or 277 counting only the distinct ones).

The product of its (nonzero) digits is 2709504, while the sum is 54.

The spelling of 21897872640 in words is "twenty-one billion, eight hundred ninety-seven million, eight hundred seventy-two thousand, six hundred forty".