21524420 has 24 divisors (see below), whose sum is σ = 45878784. Its totient is φ = 8480736.

The previous prime is 21524401. The next prime is 21524423. The reversal of 21524420 is 2442512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21524392 and 21524401.

It is not an unprimeable number, because it can be changed into a prime (21524423) 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, 6692 + ... + 9371.

It is an arithmetic number, because the mean of its divisors is an integer number (1911616).

Almost surely, 2^21524420 is an apocalyptic number.

21524420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21524420 is an abundant number, since it is smaller than the sum of its proper divisors (24354364).

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

21524420 is a wasteful number, since it uses less digits than its factorization.

21524420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16139 (or 16137 counting only the distinct ones).

The product of its (nonzero) digits is 640, while the sum is 20.

The square root of 21524420 is about 4639.4417767658. The cubic root of 21524420 is about 278.1701251530.

Adding to 21524420 its reverse (2442512), we get a palindrome (23966932).

The spelling of 21524420 in words is "twenty-one million, five hundred twenty-four thousand, four hundred twenty".