21012340 has 48 divisors (see below), whose sum is σ = 48771072. Its totient is φ = 7563776.

The previous prime is 21012331. The next prime is 21012349. The reversal of 21012340 is 4321012.

It is an interprime number because it is at equal distance from previous prime (21012331) and next prime (21012349).

It is a self number, because there is not a number n which added to its sum of digits gives 21012340.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012349) 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, 6477 + ... + 9163.

It is an arithmetic number, because the mean of its divisors is an integer number (1016064).

Almost surely, 2^21012340 is an apocalyptic number.

21012340 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 21012340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24385536).

21012340 is an abundant number, since it is smaller than the sum of its proper divisors (27758732).

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

21012340 is a wasteful number, since it uses less digits than its factorization.

21012340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2736 (or 2734 counting only the distinct ones).

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 21012340 is about 4583.9219016035. The cubic root of 21012340 is about 275.9464469365.

Adding to 21012340 its reverse (4321012), we get a palindrome (25333352).

The spelling of 21012340 in words is "twenty-one million, twelve thousand, three hundred forty".