21554509761 has 24 divisors (see below), whose sum is σ = 31574148320. Its totient is φ = 14166830016.

The previous prime is 21554509751. The next prime is 21554509771. The reversal of 21554509761 is 16790545512.

It is a happy number.

21554509761 is a `hidden beast` number, since 2 + 1 + 55 + 450 + 97 + 61 = 666.

It is an interprime number because it is at equal distance from previous prime (21554509751) and next prime (21554509771).

It is not a de Polignac number, because 21554509761 - 2¹⁹ = 21553985473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21554509721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1978050 + ... + 1988916.

Almost surely, 2^21554509761 is an apocalyptic number.

It is an amenable number.

21554509761 is a deficient number, since it is larger than the sum of its proper divisors (10019638559).

21554509761 is a wasteful number, since it uses less digits than its factorization.

21554509761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13965 (or 13962 counting only the distinct ones).

The product of its (nonzero) digits is 378000, while the sum is 45.

The spelling of 21554509761 in words is "twenty-one billion, five hundred fifty-four million, five hundred nine thousand, seven hundred sixty-one".