21157206 has 16 divisors (see below), whose sum is σ = 48359424. Its totient is φ = 6044904.

The previous prime is 21157139. The next prime is 21157207. The reversal of 21157206 is 60275112.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157207) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 251830 + ... + 251913.

It is an arithmetic number, because the mean of its divisors is an integer number (3022464).

Almost surely, 2^21157206 is an apocalyptic number.

21157206 is an abundant number, since it is smaller than the sum of its proper divisors (27202218).

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

21157206 is a wasteful number, since it uses less digits than its factorization.

21157206 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503755.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 21157206 is about 4599.6962943221. The cubic root of 21157206 is about 276.5791503972.

The spelling of 21157206 in words is "twenty-one million, one hundred fifty-seven thousand, two hundred six".