21153220251 has 8 divisors (see below), whose sum is σ = 28207087104. Its totient is φ = 14100750120.

The previous prime is 21153220247. The next prime is 21153220261. The reversal of 21153220251 is 15202235112.

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

It is not a de Polignac number, because 21153220251 - 2² = 21153220247 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21153220261) 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, 313315 + ... + 374796.

It is an arithmetic number, because the mean of its divisors is an integer number (3525885888).

Almost surely, 2^21153220251 is an apocalyptic number.

21153220251 is a deficient number, since it is larger than the sum of its proper divisors (7053866853).

21153220251 is a wasteful number, since it uses less digits than its factorization.

21153220251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 698361.

The product of its (nonzero) digits is 1200, while the sum is 24.

Adding to 21153220251 its reverse (15202235112), we get a palindrome (36355455363).

The spelling of 21153220251 in words is "twenty-one billion, one hundred fifty-three million, two hundred twenty thousand, two hundred fifty-one".