21764660 has 12 divisors (see below), whose sum is σ = 45705828. Its totient is φ = 8705856.

The previous prime is 21764653. The next prime is 21764663. The reversal of 21764660 is 6646712.

It can be written as a sum of positive squares in 2 ways, for example, as 2439844 + 19324816 = 1562^2 + 4396^2 .

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21764663) 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, 544097 + ... + 544136.

It is an arithmetic number, because the mean of its divisors is an integer number (3808819).

Almost surely, 2^21764660 is an apocalyptic number.

21764660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21764660 is an abundant number, since it is smaller than the sum of its proper divisors (23941168).

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

21764660 is a wasteful number, since it uses less digits than its factorization.

21764660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1088242 (or 1088240 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 32.

The square root of 21764660 is about 4665.2609787664. The cubic root of 21764660 is about 279.2012097549.

The spelling of 21764660 in words is "twenty-one million, seven hundred sixty-four thousand, six hundred sixty".