21738810 has 16 divisors (see below), whose sum is σ = 52173216. Its totient is φ = 5797008.

The previous prime is 21738809. The next prime is 21738811. The reversal of 21738810 is 1883712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21738809) and next prime (21738811).

It is a super-2 number, since 2×21738810² = 945151720432200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (30), and also a Moran number because the ratio is a prime number: 724627 = 21738810 / (2 + 1 + 7 + 3 + 8 + 8 + 1 + 0).

It is not an unprimeable number, because it can be changed into a prime (21738811) 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, 362284 + ... + 362343.

It is an arithmetic number, because the mean of its divisors is an integer number (3260826).

Almost surely, 2^21738810 is an apocalyptic number.

21738810 is an abundant number, since it is smaller than the sum of its proper divisors (30434406).

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

21738810 is a wasteful number, since it uses less digits than its factorization.

21738810 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 724637.

The product of its (nonzero) digits is 2688, while the sum is 30.

The square root of 21738810 is about 4662.4896782728. The cubic root of 21738810 is about 279.0906297211.

The spelling of 21738810 in words is "twenty-one million, seven hundred thirty-eight thousand, eight hundred ten".