21021828565 has 8 divisors (see below), whose sum is σ = 25243144920. Its totient is φ = 16806162432.

The previous prime is 21021828563. The next prime is 21021828577. The reversal of 21021828565 is 56582812012.

It can be written as a sum of positive squares in 4 ways, for example, as 4659837169 + 16361991396 = 68263^2 + 127914^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21021828565 - 2¹ = 21021828563 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021828563) 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, 1404364 + ... + 1419253.

It is an arithmetic number, because the mean of its divisors is an integer number (3155393115).

Almost surely, 2^21021828565 is an apocalyptic number.

It is an amenable number.

21021828565 is a deficient number, since it is larger than the sum of its proper divisors (4221316355).

21021828565 is a wasteful number, since it uses less digits than its factorization.

21021828565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2825111.

The product of its (nonzero) digits is 76800, while the sum is 40.

The spelling of 21021828565 in words is "twenty-one billion, twenty-one million, eight hundred twenty-eight thousand, five hundred sixty-five".