21265761864 has 16 divisors (see below), whose sum is σ = 53164404720. Its totient is φ = 7088587280.

The previous prime is 21265761863. The next prime is 21265761871. The reversal of 21265761864 is 46816756212.

It is not an unprimeable number, because it can be changed into a prime (21265761863) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 443036682 + ... + 443036729.

It is an arithmetic number, because the mean of its divisors is an integer number (3322775295).

Almost surely, 2^21265761864 is an apocalyptic number.

21265761864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21265761864 is an abundant number, since it is smaller than the sum of its proper divisors (31898642856).

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

21265761864 is a wasteful number, since it uses less digits than its factorization.

21265761864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 886073420 (or 886073416 counting only the distinct ones).

The product of its digits is 967680, while the sum is 48.

The spelling of 21265761864 in words is "twenty-one billion, two hundred sixty-five million, seven hundred sixty-one thousand, eight hundred sixty-four".