21425540 has 24 divisors (see below), whose sum is σ = 47362560. Its totient is φ = 8119008.

The previous prime is 21425539. The next prime is 21425549. The reversal of 21425540 is 4552412.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21425549) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27812 + ... + 28571.

It is an arithmetic number, because the mean of its divisors is an integer number (1973440).

Almost surely, 2^21425540 is an apocalyptic number.

21425540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21425540 is an abundant number, since it is smaller than the sum of its proper divisors (25937020).

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

21425540 is a wasteful number, since it uses less digits than its factorization.

21425540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 56411 (or 56409 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21425540 is about 4628.7730555732. The cubic root of 21425540 is about 277.7435137589.

Adding to 21425540 its reverse (4552412), we get a palindrome (25977952).

The spelling of 21425540 in words is "twenty-one million, four hundred twenty-five thousand, five hundred forty".