21118401656551 has 4 divisors (see below), whose sum is σ = 22229896480600. Its totient is φ = 20006906832504.

The previous prime is 21118401656531. The next prime is 21118401656557. The reversal of 21118401656551 is 15565610481112.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21118401656551 - 2²³ = 21118393267943 is a prime.

It is a super-2 number, since 2×21118401656551² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118401656557) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 555747411996 + ... + 555747412033.

It is an arithmetic number, because the mean of its divisors is an integer number (5557474120150).

Almost surely, 2^{21118401656551} is an apocalyptic number.

21118401656551 is a deficient number, since it is larger than the sum of its proper divisors (1111494824049).

21118401656551 is a wasteful number, since it uses less digits than its factorization.

21118401656551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1111494824048.

The product of its (nonzero) digits is 288000, while the sum is 46.

The spelling of 21118401656551 in words is "twenty-one trillion, one hundred eighteen billion, four hundred one million, six hundred fifty-six thousand, five hundred fifty-one".