21253415665 has 8 divisors (see below), whose sum is σ = 25581152448. Its totient is φ = 16951363440.

The previous prime is 21253415663. The next prime is 21253415681. The reversal of 21253415665 is 56651435212.

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

It is not a de Polignac number, because 21253415665 - 2¹ = 21253415663 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21253415663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6419317 + ... + 6422626.

It is an arithmetic number, because the mean of its divisors is an integer number (3197644056).

Almost surely, 2^21253415665 is an apocalyptic number.

It is an amenable number.

21253415665 is a deficient number, since it is larger than the sum of its proper divisors (4327736783).

21253415665 is a wasteful number, since it uses less digits than its factorization.

21253415665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12842279.

The product of its digits is 216000, while the sum is 40.

The spelling of 21253415665 in words is "twenty-one billion, two hundred fifty-three million, four hundred fifteen thousand, six hundred sixty-five".