21551257667 has 4 divisors (see below), whose sum is σ = 21552217560. Its totient is φ = 21550297776.

The previous prime is 21551257657. The next prime is 21551257687. The reversal of 21551257667 is 76675215512.

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 21551257667 - 2⁶ = 21551257603 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21551257657) 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, 445442 + ... + 491447.

It is an arithmetic number, because the mean of its divisors is an integer number (5388054390).

Almost surely, 2^21551257667 is an apocalyptic number.

21551257667 is a deficient number, since it is larger than the sum of its proper divisors (959893).

21551257667 is an equidigital number, since it uses as much as digits as its factorization.

21551257667 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 959892.

The product of its digits is 882000, while the sum is 47.

The spelling of 21551257667 in words is "twenty-one billion, five hundred fifty-one million, two hundred fifty-seven thousand, six hundred sixty-seven".