21737664 has 84 divisors (see below), whose sum is σ = 67123056. Its totient is φ = 6686208.

The previous prime is 21737663. The next prime is 21737687. The reversal of 21737664 is 46673712.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21737663) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 6037 + ... + 8939.

It is an arithmetic number, because the mean of its divisors is an integer number (799084).

Almost surely, 2^21737664 is an apocalyptic number.

21737664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21737664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33561528).

21737664 is an abundant number, since it is smaller than the sum of its proper divisors (45385392).

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

21737664 is a wasteful number, since it uses less digits than its factorization.

21737664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2934 (or 2921 counting only the distinct ones).

The product of its digits is 42336, while the sum is 36.

The square root of 21737664 is about 4662.3667809386. The cubic root of 21737664 is about 279.0857253820.

The spelling of 21737664 in words is "twenty-one million, seven hundred thirty-seven thousand, six hundred sixty-four".