21623947 has 8 divisors (see below), whose sum is σ = 22629456. Its totient is φ = 20640672.

The previous prime is 21623939. The next prime is 21623963. The reversal of 21623947 is 74932612.

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

It is not a de Polignac number, because 21623947 - 2³ = 21623939 is a prime.

It is a super-3 number, since 3×21623947³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21623347) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3553 + ... + 7474.

It is an arithmetic number, because the mean of its divisors is an integer number (2828682).

Almost surely, 2^21623947 is an apocalyptic number.

21623947 is a deficient number, since it is larger than the sum of its proper divisors (1005509).

21623947 is a wasteful number, since it uses less digits than its factorization.

21623947 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11117.

The product of its digits is 18144, while the sum is 34.

The square root of 21623947 is about 4650.1555887949. The cubic root of 21623947 is about 278.5982106432.

The spelling of 21623947 in words is "twenty-one million, six hundred twenty-three thousand, nine hundred forty-seven".