21012768 has 108 divisors (see below), whose sum is σ = 69557670. Its totient is φ = 5999616.

The previous prime is 21012749. The next prime is 21012773. The reversal of 21012768 is 86721012.

It can be written as a sum of positive squares in only one way, i.e., 19820304 + 1192464 = 4452^2 + 1092^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 13368 + ... + 14856.

Almost surely, 2^21012768 is an apocalyptic number.

21012768 is a gapful number since it is divisible by the number (28) 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 21012768, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34778835).

21012768 is an abundant number, since it is smaller than the sum of its proper divisors (48544902).

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

21012768 is a wasteful number, since it uses less digits than its factorization.

21012768 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1519 (or 1501 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 21012768 is about 4583.9685862798. The cubic root of 21012768 is about 275.9483205066.

The spelling of 21012768 in words is "twenty-one million, twelve thousand, seven hundred sixty-eight".