21495001644 has 192 divisors, whose sum is σ = 59505600000. Its totient is φ = 6691030272.

The previous prime is 21495001643. The next prime is 21495001673. The reversal of 21495001644 is 44610059412.

21495001644 is a `hidden beast` number, since 2 + 1 + 4 + 9 + 5 + 0 + 0 + 1 + 644 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 21495001599 and 21495001608.

It is not an unprimeable number, because it can be changed into a prime (21495001643) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 70016139 + ... + 70016445.

It is an arithmetic number, because the mean of its divisors is an integer number (309925000).

Almost surely, 2^21495001644 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21495001644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29752800000).

21495001644 is an abundant number, since it is smaller than the sum of its proper divisors (38010598356).

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

21495001644 is a wasteful number, since it uses less digits than its factorization.

21495001644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 717 (or 709 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The spelling of 21495001644 in words is "twenty-one billion, four hundred ninety-five million, one thousand, six hundred forty-four".