21577971 has 4 divisors (see below), whose sum is σ = 28770632. Its totient is φ = 14385312.

The previous prime is 21577951. The next prime is 21577973. The reversal of 21577971 is 17977512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21577971 - 2⁹ = 21577459 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21577973) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 3596326 + ... + 3596331.

It is an arithmetic number, because the mean of its divisors is an integer number (7192658).

Almost surely, 2^21577971 is an apocalyptic number.

21577971 is a deficient number, since it is larger than the sum of its proper divisors (7192661).

21577971 is an equidigital number, since it uses as much as digits as its factorization.

21577971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7192660.

The product of its digits is 30870, while the sum is 39.

The square root of 21577971 is about 4645.2094678281. The cubic root of 21577971 is about 278.4006222943.

The spelling of 21577971 in words is "twenty-one million, five hundred seventy-seven thousand, nine hundred seventy-one".