21263538 has 8 divisors (see below), whose sum is σ = 42527088. Its totient is φ = 7087844.

The previous prime is 21263537. The next prime is 21263579. The reversal of 21263538 is 83536212.

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

21263538 is an admirable number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21263533) 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 3 ways as a sum of consecutive naturals, for example, 1771956 + ... + 1771967.

It is an arithmetic number, because the mean of its divisors is an integer number (5315886).

Almost surely, 2^21263538 is an apocalyptic number.

21263538 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21263538 is a wasteful number, since it uses less digits than its factorization.

21263538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3543928.

The product of its digits is 8640, while the sum is 30.

The square root of 21263538 is about 4611.2403971166. The cubic root of 21263538 is about 277.0417206596.

The spelling of 21263538 in words is "twenty-one million, two hundred sixty-three thousand, five hundred thirty-eight".