921640 has 16 divisors (see below), whose sum is σ = 2073780. Its totient is φ = 368640.

The previous prime is 921637. The next prime is 921643. The reversal of 921640 is 46129.

921640 = T₅₉ + T₆₀ + ... + T₁₇₈.

It is an interprime number because it is at equal distance from previous prime (921637) and next prime (921643).

It can be written as a sum of positive squares in 2 ways, for example, as 872356 + 49284 = 934^2 + 222^2 .

It is not an unprimeable number, because it can be changed into a prime (921643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 11481 + ... + 11560.

2⁹²¹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

921640 is an abundant number, since it is smaller than the sum of its proper divisors (1152140).

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

921640 is a wasteful number, since it uses less digits than its factorization.

921640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23052 (or 23048 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 921640 is about 960.0208331073. The cubic root of 921640 is about 97.3166398259.

Adding to 921640 its reverse (46129), we get a palindrome (967769).

The spelling of 921640 in words is "nine hundred twenty-one thousand, six hundred forty".