21878001 has 12 divisors (see below), whose sum is σ = 31740228. Its totient is φ = 14521344.

The previous prime is 21877951. The next prime is 21878047. The reversal of 21878001 is 10087812.

It can be written as a sum of positive squares in 2 ways, for example, as 9090225 + 12787776 = 3015^2 + 3576^2 .

It is not a de Polignac number, because 21878001 - 2⁹ = 21877489 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21878071) 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, 3120 + ... + 7313.

It is an arithmetic number, because the mean of its divisors is an integer number (2645019).

Almost surely, 2^21878001 is an apocalyptic number.

It is an amenable number.

21878001 is a deficient number, since it is larger than the sum of its proper divisors (9862227).

21878001 is a wasteful number, since it uses less digits than its factorization.

21878001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10672 (or 10669 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 27.

The square root of 21878001 is about 4677.3925428598. The cubic root of 21878001 is about 279.6850242137.

The spelling of 21878001 in words is "twenty-one million, eight hundred seventy-eight thousand, one".