21764280 has 64 divisors (see below), whose sum is σ = 66291840. Its totient is φ = 5715072.

The previous prime is 21764273. The next prime is 21764287. The reversal of 21764280 is 8246712.

It is an interprime number because it is at equal distance from previous prime (21764273) and next prime (21764287).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21764287) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6687 + ... + 9393.

It is an arithmetic number, because the mean of its divisors is an integer number (1035810).

Almost surely, 2^21764280 is an apocalyptic number.

21764280 is a gapful number since it is divisible by the number (20) 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 21764280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33145920).

21764280 is an abundant number, since it is smaller than the sum of its proper divisors (44527560).

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

21764280 is a wasteful number, since it uses less digits than its factorization.

21764280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2788 (or 2784 counting only the distinct ones).

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 21764280 is about 4665.2202520353. The cubic root of 21764280 is about 279.1995848413.

The spelling of 21764280 in words is "twenty-one million, seven hundred sixty-four thousand, two hundred eighty".