21216509247 has 32 divisors (see below), whose sum is σ = 29222504640. Its totient is φ = 13686865920.

The previous prime is 21216509221. The next prime is 21216509263. The reversal of 21216509247 is 74290561212.

It is not a de Polignac number, because 21216509247 - 2⁸ = 21216508991 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216509267) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2829279 + ... + 2836767.

It is an arithmetic number, because the mean of its divisors is an integer number (913203270).

Almost surely, 2^21216509247 is an apocalyptic number.

21216509247 is a deficient number, since it is larger than the sum of its proper divisors (8005995393).

21216509247 is a wasteful number, since it uses less digits than its factorization.

21216509247 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7803.

The product of its (nonzero) digits is 60480, while the sum is 39.

The spelling of 21216509247 in words is "twenty-one billion, two hundred sixteen million, five hundred nine thousand, two hundred forty-seven".