21639677 has 8 divisors (see below), whose sum is σ = 22438080. Its totient is φ = 20854240.

The previous prime is 21639647. The next prime is 21639679. The reversal of 21639677 is 77693612.

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

It is not a de Polignac number, because 21639677 - 2¹⁶ = 21574141 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (41).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639679) 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, 224 + ... + 6582.

It is an arithmetic number, because the mean of its divisors is an integer number (2804760).

Almost surely, 2^21639677 is an apocalyptic number.

It is an amenable number.

21639677 is a deficient number, since it is larger than the sum of its proper divisors (798403).

21639677 is an equidigital number, since it uses as much as digits as its factorization.

21639677 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6483.

The product of its digits is 95256, while the sum is 41.

The square root of 21639677 is about 4651.8466225790. The cubic root of 21639677 is about 278.6657482310.

It can be divided in two parts, 216 and 39677, that added together give a palindrome (39893).

The spelling of 21639677 in words is "twenty-one million, six hundred thirty-nine thousand, six hundred seventy-seven".