21620447 has 4 divisors (see below), whose sum is σ = 22892256. Its totient is φ = 20348640.

The previous prime is 21620419. The next prime is 21620453. The reversal of 21620447 is 74402612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21620447 - 2⁶ = 21620383 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21620497) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 635879 + ... + 635912.

It is an arithmetic number, because the mean of its divisors is an integer number (5723064).

Almost surely, 2^21620447 is an apocalyptic number.

21620447 is a deficient number, since it is larger than the sum of its proper divisors (1271809).

21620447 is a wasteful number, since it uses less digits than its factorization.

21620447 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1271808.

The product of its (nonzero) digits is 2688, while the sum is 26.

The square root of 21620447 is about 4649.7792420716. The cubic root of 21620447 is about 278.5831787536.

The spelling of 21620447 in words is "twenty-one million, six hundred twenty thousand, four hundred forty-seven".