21217204239 has 16 divisors (see below), whose sum is σ = 35270158080. Its totient is φ = 11021924160.

The previous prime is 21217204237. The next prime is 21217204241. The reversal of 21217204239 is 93240271212.

It is an interprime number because it is at equal distance from previous prime (21217204237) and next prime (21217204241).

It is not a de Polignac number, because 21217204239 - 2¹ = 21217204237 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217204237) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45924454 + ... + 45924915.

It is an arithmetic number, because the mean of its divisors is an integer number (2204384880).

Almost surely, 2^21217204239 is an apocalyptic number.

21217204239 is a deficient number, since it is larger than the sum of its proper divisors (14052953841).

21217204239 is a wasteful number, since it uses less digits than its factorization.

21217204239 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 91849390.

The product of its (nonzero) digits is 12096, while the sum is 33.

It can be divided in two parts, 21217 and 204239, that added together give a triangular number (225456 = T₆₇₁).

The spelling of 21217204239 in words is "twenty-one billion, two hundred seventeen million, two hundred four thousand, two hundred thirty-nine".