21151121621 has 8 divisors (see below), whose sum is σ = 24176708544. Its totient is φ = 18126534240.

The previous prime is 21151121611. The next prime is 21151121623. The reversal of 21151121621 is 12612115112.

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 a de Polignac number, because none of the positive numbers 2^k-21151121621 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 (21151121623) 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, 203975 + ... + 289668.

It is an arithmetic number, because the mean of its divisors is an integer number (3022088568).

Almost surely, 2^21151121621 is an apocalyptic number.

It is an amenable number.

21151121621 is a deficient number, since it is larger than the sum of its proper divisors (3025586923).

21151121621 is an equidigital number, since it uses as much as digits as its factorization.

21151121621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 499771.

The product of its digits is 240, while the sum is 23.

Adding to 21151121621 its reverse (12612115112), we get a palindrome (33763236733).

The spelling of 21151121621 in words is "twenty-one billion, one hundred fifty-one million, one hundred twenty-one thousand, six hundred twenty-one".