21920591 has 24 divisors (see below), whose sum is σ = 28279296. Its totient is φ = 16798320.

The previous prime is 21920573. The next prime is 21920621. The reversal of 21920591 is 19502912.

It is not a de Polignac number, because 21920591 - 2¹⁰ = 21919567 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 (21920501) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35810 + ... + 36416.

It is an arithmetic number, because the mean of its divisors is an integer number (1178304).

Almost surely, 2^21920591 is an apocalyptic number.

21920591 is a deficient number, since it is larger than the sum of its proper divisors (6358705).

21920591 is a wasteful number, since it uses less digits than its factorization.

21920591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 699 (or 692 counting only the distinct ones).

The product of its (nonzero) digits is 1620, while the sum is 29.

The square root of 21920591 is about 4681.9430795344. The cubic root of 21920591 is about 279.8663945920.

The spelling of 21920591 in words is "twenty-one million, nine hundred twenty thousand, five hundred ninety-one".