21157730 has 16 divisors (see below), whose sum is σ = 41546304. Its totient is φ = 7693680.

The previous prime is 21157699. The next prime is 21157739. The reversal of 21157730 is 3775112.

It is a self number, because there is not a number n which added to its sum of digits gives 21157730.

It is not an unprimeable number, because it can be changed into a prime (21157739) 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, 96062 + ... + 96281.

It is an arithmetic number, because the mean of its divisors is an integer number (2596644).

Almost surely, 2^21157730 is an apocalyptic number.

21157730 is a deficient number, since it is larger than the sum of its proper divisors (20388574).

21157730 is a wasteful number, since it uses less digits than its factorization.

21157730 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 192361.

The product of its (nonzero) digits is 1470, while the sum is 26.

The square root of 21157730 is about 4599.7532542518. The cubic root of 21157730 is about 276.5814337214.

It can be divided in two parts, 21 and 157730, that added together give a palindrome (157751).

The spelling of 21157730 in words is "twenty-one million, one hundred fifty-seven thousand, seven hundred thirty".