21425040 has 320 divisors, whose sum is σ = 91660800. Its totient is φ = 4478976.

The previous prime is 21425023. The next prime is 21425057. The reversal of 21425040 is 4052412.

It is an interprime number because it is at equal distance from previous prime (21425023) and next prime (21425057).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 196506 + ... + 196614.

It is an arithmetic number, because the mean of its divisors is an integer number (286440).

Almost surely, 2^21425040 is an apocalyptic number.

21425040 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 21425040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (45830400).

21425040 is an abundant number, since it is smaller than the sum of its proper divisors (70235760).

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

21425040 is a wasteful number, since it uses less digits than its factorization.

21425040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 139 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 18.

The square root of 21425040 is about 4628.7190452651. The cubic root of 21425040 is about 277.7413532091.

Adding to 21425040 its reverse (4052412), we get a palindrome (25477452).

The spelling of 21425040 in words is "twenty-one million, four hundred twenty-five thousand, forty".