21425640 has 64 divisors (see below), whose sum is σ = 65352960. Its totient is φ = 5617920.

The previous prime is 21425639. The next prime is 21425641. The reversal of 21425640 is 4652412.

It is an interprime number because it is at equal distance from previous prime (21425639) and next prime (21425641).

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 21425640.

It is not an unprimeable number, because it can be changed into a prime (21425641) 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, 5857 + ... + 8783.

It is an arithmetic number, because the mean of its divisors is an integer number (1021140).

Almost surely, 2^21425640 is an apocalyptic number.

21425640 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 21425640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32676480).

21425640 is an abundant number, since it is smaller than the sum of its proper divisors (43927320).

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

21425640 is a wasteful number, since it uses less digits than its factorization.

21425640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3002 (or 2998 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 21425640 is about 4628.7838575591. The cubic root of 21425640 is about 277.7439458648.

The spelling of 21425640 in words is "twenty-one million, four hundred twenty-five thousand, six hundred forty".