21489091965 has 128 divisors (see below), whose sum is σ = 43274649600. Its totient is φ = 10023264000.

The previous prime is 21489091963. The next prime is 21489091969. The reversal of 21489091965 is 56919098412.

It is not a de Polignac number, because 21489091965 - 2¹ = 21489091963 is a prime.

It is a super-4 number, since 4×21489091965⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21489091963) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 8331046 + ... + 8333624.

It is an arithmetic number, because the mean of its divisors is an integer number (338083200).

Almost surely, 2^21489091965 is an apocalyptic number.

It is an amenable number.

21489091965 is an abundant number, since it is smaller than the sum of its proper divisors (21785557635).

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

21489091965 is a wasteful number, since it uses less digits than its factorization.

21489091965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2816 (or 2810 counting only the distinct ones).

The product of its (nonzero) digits is 1399680, while the sum is 54.

The spelling of 21489091965 in words is "twenty-one billion, four hundred eighty-nine million, ninety-one thousand, nine hundred sixty-five".