21393780 has 24 divisors (see below), whose sum is σ = 59902752. Its totient is φ = 5704992.

The previous prime is 21393773. The next prime is 21393809. The reversal of 21393780 is 8739312.

It is a zygodrome in base 9.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 178222 + ... + 178341.

It is an arithmetic number, because the mean of its divisors is an integer number (2495948).

Almost surely, 2^21393780 is an apocalyptic number.

21393780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21393780 is an abundant number, since it is smaller than the sum of its proper divisors (38508972).

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

21393780 is a wasteful number, since it uses less digits than its factorization.

21393780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 356575 (or 356573 counting only the distinct ones).

The product of its (nonzero) digits is 9072, while the sum is 33.

The square root of 21393780 is about 4625.3410685051. The cubic root of 21393780 is about 277.6062088378.

The spelling of 21393780 in words is "twenty-one million, three hundred ninety-three thousand, seven hundred eighty".