21019680 has 144 divisors (see below), whose sum is σ = 78309504. Its totient is φ = 5091840.

The previous prime is 21019657. The next prime is 21019699. The reversal of 21019680 is 8691012.

21019680 = 591² + 592² + ... + 645².

It is a tau number, because it is divible by the number of its divisors (144).

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15177 + ... + 16503.

It is an arithmetic number, because the mean of its divisors is an integer number (543816).

Almost surely, 2^21019680 is an apocalyptic number.

21019680 is a gapful number since it is divisible by the number (20) 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 21019680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39154752).

21019680 is an abundant number, since it is smaller than the sum of its proper divisors (57289824).

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

21019680 is a wasteful number, since it uses less digits than its factorization.

21019680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1359 (or 1348 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 21019680 is about 4584.7224561581. The cubic root of 21019680 is about 275.9785742662.

It can be divided in two parts, 210196 and 80, that added together give a triangular number (210276 = T₆₄₈).

The spelling of 21019680 in words is "twenty-one million, nineteen thousand, six hundred eighty".