21533457 has 16 divisors (see below), whose sum is σ = 32402880. Its totient is φ = 12600000.

The previous prime is 21533443. The next prime is 21533459. The reversal of 21533457 is 75433512.

It is not a de Polignac number, because 21533457 - 2¹⁴ = 21517073 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21533459) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10294 + ... + 12207.

It is an arithmetic number, because the mean of its divisors is an integer number (2025180).

Almost surely, 2^21533457 is an apocalyptic number.

It is an amenable number.

21533457 is a deficient number, since it is larger than the sum of its proper divisors (10869423).

21533457 is a wasteful number, since it uses less digits than its factorization.

21533457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22544.

The product of its digits is 12600, while the sum is 30.

The square root of 21533457 is about 4640.4156063870. The cubic root of 21533457 is about 278.2090494956.

Adding to 21533457 its reverse (75433512), we get a palindrome (96966969).

The spelling of 21533457 in words is "twenty-one million, five hundred thirty-three thousand, four hundred fifty-seven".