21021220591 has 16 divisors (see below), whose sum is σ = 24134492160. Its totient is φ = 17935639200.

The previous prime is 21021220547. The next prime is 21021220601. The reversal of 21021220591 is 19502212012.

It is not a de Polignac number, because 21021220591 - 2¹⁷ = 21021089519 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 (21021220501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2227080 + ... + 2236498.

It is an arithmetic number, because the mean of its divisors is an integer number (1508405760).

Almost surely, 2^21021220591 is an apocalyptic number.

21021220591 is a deficient number, since it is larger than the sum of its proper divisors (3113271569).

21021220591 is a wasteful number, since it uses less digits than its factorization.

21021220591 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10854.

The product of its (nonzero) digits is 720, while the sum is 25.

The spelling of 21021220591 in words is "twenty-one billion, twenty-one million, two hundred twenty thousand, five hundred ninety-one".