21520475 has 6 divisors (see below), whose sum is σ = 26685420. Its totient is φ = 17216360.

The previous prime is 21520463. The next prime is 21520481. The reversal of 21520475 is 57402512.

It is not a de Polignac number, because 21520475 - 2⁴ = 21520459 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 430385 + ... + 430434.

It is an arithmetic number, because the mean of its divisors is an integer number (4447570).

Almost surely, 2^21520475 is an apocalyptic number.

21520475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21520475 is a deficient number, since it is larger than the sum of its proper divisors (5164945).

21520475 is an equidigital number, since it uses as much as digits as its factorization.

21520475 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 860829 (or 860824 counting only the distinct ones).

The product of its (nonzero) digits is 2800, while the sum is 26.

The square root of 21520475 is about 4639.0165983751. The cubic root of 21520475 is about 278.1531297559.

Adding to 21520475 its reverse (57402512), we get a palindrome (78922987).

The spelling of 21520475 in words is "twenty-one million, five hundred twenty thousand, four hundred seventy-five".