21011720280 has 64 divisors (see below), whose sum is σ = 63053998560. Its totient is φ = 5601451008.

The previous prime is 21011720267. The next prime is 21011720381. The reversal of 21011720280 is 8202711012.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21011720280.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 406794 + ... + 455526.

Almost surely, 2^21011720280 is an apocalyptic number.

21011720280 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21011720280 is an abundant number, since it is smaller than the sum of its proper divisors (42042278280).

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

21011720280 is a wasteful number, since it uses less digits than its factorization.

21011720280 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52340 (or 52336 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 24.

The spelling of 21011720280 in words is "twenty-one billion, eleven million, seven hundred twenty thousand, two hundred eighty".