21213945551 has 8 divisors (see below), whose sum is σ = 21537459120. Its totient is φ = 20890634688.

The previous prime is 21213945547. The next prime is 21213945559. The reversal of 21213945551 is 15554931212.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21213945551 - 2² = 21213945547 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213945559) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 167315 + ... + 265371.

It is an arithmetic number, because the mean of its divisors is an integer number (2692182390).

Almost surely, 2^21213945551 is an apocalyptic number.

21213945551 is a deficient number, since it is larger than the sum of its proper divisors (323513569).

21213945551 is an equidigital number, since it uses as much as digits as its factorization.

21213945551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 101353.

The product of its digits is 54000, while the sum is 38.

The spelling of 21213945551 in words is "twenty-one billion, two hundred thirteen million, nine hundred forty-five thousand, five hundred fifty-one".