21641955 has 8 divisors (see below), whose sum is σ = 34627152. Its totient is φ = 11542368.

The previous prime is 21641947. The next prime is 21641957. The reversal of 21641955 is 55914612.

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

It is not a de Polignac number, because 21641955 - 2³ = 21641947 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21641957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 721384 + ... + 721413.

It is an arithmetic number, because the mean of its divisors is an integer number (4328394).

Almost surely, 2^21641955 is an apocalyptic number.

21641955 is a deficient number, since it is larger than the sum of its proper divisors (12985197).

21641955 is a wasteful number, since it uses less digits than its factorization.

21641955 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1442805.

The product of its digits is 10800, while the sum is 33.

The square root of 21641955 is about 4652.0914651369. The cubic root of 21641955 is about 278.6755262313.

The spelling of 21641955 in words is "twenty-one million, six hundred forty-one thousand, nine hundred fifty-five".