21820825465 has 4 divisors (see below), whose sum is σ = 26184990564. Its totient is φ = 17456660368.

The previous prime is 21820825427. The next prime is 21820825471. The reversal of 21820825465 is 56452802812.

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

It can be written as a sum of positive squares in 2 ways, for example, as 11419273321 + 10401552144 = 106861^2 + 101988^2 .

It is a cyclic number.

It is not a de Polignac number, because 21820825465 - 2¹⁹ = 21820301177 is a prime.

It is a super-2 number, since 2×21820825465² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2182082542 + ... + 2182082551.

It is an arithmetic number, because the mean of its divisors is an integer number (6546247641).

Almost surely, 2^21820825465 is an apocalyptic number.

It is an amenable number.

21820825465 is a deficient number, since it is larger than the sum of its proper divisors (4364165099).

21820825465 is an equidigital number, since it uses as much as digits as its factorization.

21820825465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4364165098.

The product of its (nonzero) digits is 307200, while the sum is 43.

The spelling of 21820825465 in words is "twenty-one billion, eight hundred twenty million, eight hundred twenty-five thousand, four hundred sixty-five".