21515440451 has 8 divisors (see below), whose sum is σ = 21613363200. Its totient is φ = 21417729480.

The previous prime is 21515440439. The next prime is 21515440493. The reversal of 21515440451 is 15404451512.

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-21515440451 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21515440411) 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, 152510 + ... + 257468.

It is an arithmetic number, because the mean of its divisors is an integer number (2701670400).

Almost surely, 2^21515440451 is an apocalyptic number.

21515440451 is a deficient number, since it is larger than the sum of its proper divisors (97922749).

21515440451 is a wasteful number, since it uses less digits than its factorization.

21515440451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105889.

The product of its (nonzero) digits is 16000, while the sum is 32.

Adding to 21515440451 its reverse (15404451512), we get a palindrome (36919891963).

The spelling of 21515440451 in words is "twenty-one billion, five hundred fifteen million, four hundred forty thousand, four hundred fifty-one".