21623121 has 48 divisors (see below), whose sum is σ = 36167040. Its totient is φ = 12337920.

The previous prime is 21623101. The next prime is 21623131. The reversal of 21623121 is 12132612.

21623121 is a `hidden beast` number, since 21 + 623 + 1 + 21 = 666.

It is not a de Polignac number, because 21623121 - 2⁶ = 21623057 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21623094 and 21623103.

It is not an unprimeable number, because it can be changed into a prime (21623101) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 157765 + ... + 157901.

It is an arithmetic number, because the mean of its divisors is an integer number (753480).

Almost surely, 2^21623121 is an apocalyptic number.

It is an amenable number.

21623121 is a deficient number, since it is larger than the sum of its proper divisors (14543919).

21623121 is a wasteful number, since it uses less digits than its factorization.

21623121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246 (or 243 counting only the distinct ones).

The product of its digits is 144, while the sum is 18.

The square root of 21623121 is about 4650.0667737141. The cubic root of 21623121 is about 278.5946632635.

Adding to 21623121 its reverse (12132612), we get a palindrome (33755733).

The spelling of 21623121 in words is "twenty-one million, six hundred twenty-three thousand, one hundred twenty-one".