21625591 has 8 divisors (see below), whose sum is σ = 24515120. Its totient is φ = 18911232.

The previous prime is 21625577. The next prime is 21625607. The reversal of 21625591 is 19552612.

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

It is not a de Polignac number, because 21625591 - 2⁵ = 21625559 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21625531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43530 + ... + 44023.

It is an arithmetic number, because the mean of its divisors is an integer number (3064390).

Almost surely, 2^21625591 is an apocalyptic number.

21625591 is a deficient number, since it is larger than the sum of its proper divisors (2889529).

21625591 is a wasteful number, since it uses less digits than its factorization.

21625591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 87585.

The product of its digits is 5400, while the sum is 31.

The square root of 21625591 is about 4650.3323537141. The cubic root of 21625591 is about 278.6052707766.

The spelling of 21625591 in words is "twenty-one million, six hundred twenty-five thousand, five hundred ninety-one".