21425581 has 8 divisors (see below), whose sum is σ = 22446720. Its totient is φ = 20411952.

The previous prime is 21425549. The next prime is 21425587. The reversal of 21425581 is 18552412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21425581 - 2⁵ = 21425549 is a prime.

It is a super-2 number, since 2×21425581² = 918111042375122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21425587) 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, 4456 + ... + 7918.

It is an arithmetic number, because the mean of its divisors is an integer number (2805840).

Almost surely, 2^21425581 is an apocalyptic number.

It is an amenable number.

21425581 is a deficient number, since it is larger than the sum of its proper divisors (1021139).

21425581 is a wasteful number, since it uses less digits than its factorization.

21425581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3755.

The product of its digits is 3200, while the sum is 28.

The square root of 21425581 is about 4628.7774843905. Note that the first 3 decimals coincide. The cubic root of 21425581 is about 277.7436909225.

Adding to 21425581 its reverse (18552412), we get a palindrome (39977993).

The spelling of 21425581 in words is "twenty-one million, four hundred twenty-five thousand, five hundred eighty-one".