21525830 has 32 divisors (see below), whose sum is σ = 40392000. Its totient is φ = 8249472.

The previous prime is 21525793. The next prime is 21525853. The reversal of 21525830 is 3852512.

It is a super-2 number, since 2×21525830² = 926722714377800, which contains 22 as substring.

It is a Curzon number.

It is a plaindrome in base 9.

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 21525830.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57524 + ... + 57896.

It is an arithmetic number, because the mean of its divisors is an integer number (1262250).

Almost surely, 2^21525830 is an apocalyptic number.

21525830 is a deficient number, since it is larger than the sum of its proper divisors (18866170).

21525830 is a wasteful number, since it uses less digits than its factorization.

21525830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 608.

The product of its (nonzero) digits is 2400, while the sum is 26.

The square root of 21525830 is about 4639.5937322141. The cubic root of 21525830 is about 278.1761990497.

The spelling of 21525830 in words is "twenty-one million, five hundred twenty-five thousand, eight hundred thirty".