21398740 has 48 divisors (see below), whose sum is σ = 51166080. Its totient is φ = 7441280.

The previous prime is 21398737. The next prime is 21398747. The reversal of 21398740 is 4789312.

It is a junction number, because it is equal to n+sod(n) for n = 21398696 and 21398705.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21398747) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2946 + ... + 7174.

It is an arithmetic number, because the mean of its divisors is an integer number (1065960).

Almost surely, 2^21398740 is an apocalyptic number.

21398740 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 21398740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25583040).

21398740 is an abundant number, since it is smaller than the sum of its proper divisors (29767340).

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

21398740 is a wasteful number, since it uses less digits than its factorization.

21398740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4272 (or 4270 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 34.

The square root of 21398740 is about 4625.8772141076. The cubic root of 21398740 is about 277.6276608735.

The spelling of 21398740 in words is "twenty-one million, three hundred ninety-eight thousand, seven hundred forty".