21639347 has 8 divisors (see below), whose sum is σ = 22822800. Its totient is φ = 20460384.

The previous prime is 21639341. The next prime is 21639361. The reversal of 21639347 is 74393612.

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 21639347 - 2⁸ = 21639091 is a prime.

It is a super-2 number, since 2×21639347² = 936522677172818, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21639341) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14429 + ... + 15857.

It is an arithmetic number, because the mean of its divisors is an integer number (2852850).

Almost surely, 2^21639347 is an apocalyptic number.

21639347 is a deficient number, since it is larger than the sum of its proper divisors (1183453).

21639347 is a wasteful number, since it uses less digits than its factorization.

21639347 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2245.

The product of its digits is 27216, while the sum is 35.

The square root of 21639347 is about 4651.8111526587. The cubic root of 21639347 is about 278.6643316947.

The spelling of 21639347 in words is "twenty-one million, six hundred thirty-nine thousand, three hundred forty-seven".