21090238464 has 64 divisors (see below), whose sum is σ = 56240039880. Its totient is φ = 7030046720.

The previous prime is 21090238439. The next prime is 21090238517. The reversal of 21090238464 is 46483209012.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8967 + ... + 205574.

Almost surely, 2^21090238464 is an apocalyptic number.

21090238464 is a gapful number since it is divisible by the number (24) 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 21090238464, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28120019940).

21090238464 is an abundant number, since it is smaller than the sum of its proper divisors (35149801416).

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

21090238464 is an frugal number, since it uses more digits than its factorization.

21090238464 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 214574 (or 214546 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 39.

The spelling of 21090238464 in words is "twenty-one billion, ninety million, two hundred thirty-eight thousand, four hundred sixty-four".