21945860 has 12 divisors (see below), whose sum is σ = 46086348. Its totient is φ = 8778336.

The previous prime is 21945853. The next prime is 21945863. The reversal of 21945860 is 6854912.

It can be written as a sum of positive squares in 2 ways, for example, as 2515396 + 19430464 = 1586^2 + 4408^2 .

It is a super-2 number, since 2×21945860² = 963241542279200, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21945860.

It is not an unprimeable number, because it can be changed into a prime (21945863) 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, 548627 + ... + 548666.

It is an arithmetic number, because the mean of its divisors is an integer number (3840529).

Almost surely, 2^21945860 is an apocalyptic number.

21945860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21945860 is an abundant number, since it is smaller than the sum of its proper divisors (24140488).

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

21945860 is a wasteful number, since it uses less digits than its factorization.

21945860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1097302 (or 1097300 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21945860 is about 4684.6408613681. The cubic root of 21945860 is about 279.9738921235.

The spelling of 21945860 in words is "twenty-one million, nine hundred forty-five thousand, eight hundred sixty".