21523020 has 48 divisors (see below), whose sum is σ = 63812448. Its totient is φ = 5401600.

The previous prime is 21523001. The next prime is 21523049. The reversal of 21523020 is 2032512.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9531 + ... + 11570.

It is an arithmetic number, because the mean of its divisors is an integer number (1329426).

Almost surely, 2^21523020 is an apocalyptic number.

21523020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21523020 is an abundant number, since it is smaller than the sum of its proper divisors (42289428).

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

21523020 is a wasteful number, since it uses less digits than its factorization.

21523020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21130 (or 21128 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 15.

The square root of 21523020 is about 4639.2908940915. The cubic root of 21523020 is about 278.1640940711.

Adding to 21523020 its reverse (2032512), we get a palindrome (23555532).

The spelling of 21523020 in words is "twenty-one million, five hundred twenty-three thousand, twenty".