21172746 has 32 divisors (see below), whose sum is σ = 48572928. Its totient is φ = 6027120.

The previous prime is 21172733. The next prime is 21172757. The reversal of 21172746 is 64727112.

It is a super-4 number, since 4×21172746⁴ (a number of 30 digits) contains 4444 as substring.

It is a Smith number, since the sum of its digits (30) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13141 + ... + 14663.

It is an arithmetic number, because the mean of its divisors is an integer number (1517904).

Almost surely, 2^21172746 is an apocalyptic number.

21172746 is an abundant number, since it is smaller than the sum of its proper divisors (27400182).

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

21172746 is a wasteful number, since it uses less digits than its factorization.

21172746 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1866.

The product of its digits is 4704, while the sum is 30.

The square root of 21172746 is about 4601.3852262118. The cubic root of 21172746 is about 276.6468497604.

Adding to 21172746 its reverse (64727112), we get a palindrome (85899858).

The spelling of 21172746 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred forty-six".