21020340 has 48 divisors (see below), whose sum is σ = 64209600. Its totient is φ = 5095680.

The previous prime is 21020339. The next prime is 21020353. The reversal of 21020340 is 4302012.

It is a Harshad number since it is a multiple of its sum of digits (12).

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, 15265 + ... + 16584.

It is an arithmetic number, because the mean of its divisors is an integer number (1337700).

Almost surely, 2^21020340 is an apocalyptic number.

21020340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21020340 is an abundant number, since it is smaller than the sum of its proper divisors (43189260).

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

21020340 is a wasteful number, since it uses less digits than its factorization.

21020340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31872 (or 31870 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 21020340 is about 4584.7944337778. The cubic root of 21020340 is about 275.9814627331.

Adding to 21020340 its reverse (4302012), we get a palindrome (25322352).

The spelling of 21020340 in words is "twenty-one million, twenty thousand, three hundred forty".