21591958 has 16 divisors (see below), whose sum is σ = 32944320. Its totient is φ = 10612296.

The previous prime is 21591949. The next prime is 21591959. The reversal of 21591958 is 85919512.

It is a self number, because there is not a number n which added to its sum of digits gives 21591958.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21591959) 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, 34573 + ... + 35191.

It is an arithmetic number, because the mean of its divisors is an integer number (2059020).

Almost surely, 2^21591958 is an apocalyptic number.

21591958 is a deficient number, since it is larger than the sum of its proper divisors (11352362).

21591958 is a wasteful number, since it uses less digits than its factorization.

21591958 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 891.

The product of its digits is 32400, while the sum is 40.

The square root of 21591958 is about 4646.7147534575. The cubic root of 21591958 is about 278.4607630807.

The spelling of 21591958 in words is "twenty-one million, five hundred ninety-one thousand, nine hundred fifty-eight".