21554006765 has 4 divisors (see below), whose sum is σ = 25864808124. Its totient is φ = 17243205408.

The previous prime is 21554006743. The next prime is 21554006779. The reversal of 21554006765 is 56760045512.

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 4617066601 + 16936940164 = 67949^2 + 130142^2 .

It is a cyclic number.

It is not a de Polignac number, because 21554006765 - 2⁶ = 21554006701 is a prime.

It is a Duffinian number.

It is a congruent 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, 2155400672 + ... + 2155400681.

It is an arithmetic number, because the mean of its divisors is an integer number (6466202031).

Almost surely, 2^21554006765 is an apocalyptic number.

It is an amenable number.

21554006765 is a deficient number, since it is larger than the sum of its proper divisors (4310801359).

21554006765 is an equidigital number, since it uses as much as digits as its factorization.

21554006765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4310801358.

The product of its (nonzero) digits is 252000, while the sum is 41.

The spelling of 21554006765 in words is "twenty-one billion, five hundred fifty-four million, six thousand, seven hundred sixty-five".