21515234 has 16 divisors (see below), whose sum is σ = 36800568. Its totient is φ = 9345792.

The previous prime is 21515233. The next prime is 21515257. The reversal of 21515234 is 43251512.

It can be written as a sum of positive squares in 4 ways, for example, as 18037009 + 3478225 = 4247^2 + 1865^2 .

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21515233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23897 + ... + 24780.

Almost surely, 2^21515234 is an apocalyptic number.

21515234 is a deficient number, since it is larger than the sum of its proper divisors (15285334).

21515234 is a wasteful number, since it uses less digits than its factorization.

21515234 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48709.

The product of its digits is 1200, while the sum is 23.

The square root of 21515234 is about 4638.4516813264. The cubic root of 21515234 is about 278.1305478673.

Adding to 21515234 its reverse (43251512), we get a palindrome (64766746).

The spelling of 21515234 in words is "twenty-one million, five hundred fifteen thousand, two hundred thirty-four".