21406391247 has 8 divisors (see below), whose sum is σ = 28750190256. Its totient is φ = 14166759872.

The previous prime is 21406391213. The next prime is 21406391261. The reversal of 21406391247 is 74219360412.

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

It is a cyclic number.

It is not a de Polignac number, because 21406391247 - 2²⁰ = 21405342671 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21406391647) 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, 26041428 + ... + 26042249.

It is an arithmetic number, because the mean of its divisors is an integer number (3593773782).

Almost surely, 2^21406391247 is an apocalyptic number.

21406391247 is a deficient number, since it is larger than the sum of its proper divisors (7343799009).

21406391247 is a wasteful number, since it uses less digits than its factorization.

21406391247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52083817.

The product of its (nonzero) digits is 72576, while the sum is 39.

The spelling of 21406391247 in words is "twenty-one billion, four hundred six million, three hundred ninety-one thousand, two hundred forty-seven".