21242400665 has 16 divisors (see below), whose sum is σ = 25642552320. Its totient is φ = 16892957760.

The previous prime is 21242400623. The next prime is 21242400703. The reversal of 21242400665 is 56600424212.

It is not a de Polignac number, because 21242400665 - 2⁶ = 21242400601 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1203776 + ... + 1221294.

It is an arithmetic number, because the mean of its divisors is an integer number (1602659520).

Almost surely, 2^21242400665 is an apocalyptic number.

It is an amenable number.

21242400665 is a deficient number, since it is larger than the sum of its proper divisors (4400151655).

21242400665 is a wasteful number, since it uses less digits than its factorization.

21242400665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18952.

The product of its (nonzero) digits is 23040, while the sum is 32.

Adding to 21242400665 its reverse (56600424212), we get a palindrome (77842824877).

The spelling of 21242400665 in words is "twenty-one billion, two hundred forty-two million, four hundred thousand, six hundred sixty-five".