21572138 has 8 divisors (see below), whose sum is σ = 36980832. Its totient is φ = 9245196.

The previous prime is 21572119. The next prime is 21572141. The reversal of 21572138 is 83127512.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21572138.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 770420 + ... + 770447.

It is an arithmetic number, because the mean of its divisors is an integer number (4622604).

Almost surely, 2^21572138 is an apocalyptic number.

21572138 is a deficient number, since it is larger than the sum of its proper divisors (15408694).

21572138 is a wasteful number, since it uses less digits than its factorization.

21572138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1540876.

The product of its digits is 3360, while the sum is 29.

The square root of 21572138 is about 4644.5815742648. The cubic root of 21572138 is about 278.3755340971.

The spelling of 21572138 in words is "twenty-one million, five hundred seventy-two thousand, one hundred thirty-eight".