21531845 has 24 divisors (see below), whose sum is σ = 27797760. Its totient is φ = 16005600.

The previous prime is 21531827. The next prime is 21531871. The reversal of 21531845 is 54813512.

It is not a de Polignac number, because 21531845 - 2¹² = 21527749 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 142520 + ... + 142670.

It is an arithmetic number, because the mean of its divisors is an integer number (1158240).

Almost surely, 2^21531845 is an apocalyptic number.

It is an amenable number.

21531845 is a deficient number, since it is larger than the sum of its proper divisors (6265915).

21531845 is a wasteful number, since it uses less digits than its factorization.

21531845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 273 (or 254 counting only the distinct ones).

The product of its digits is 4800, while the sum is 29.

The square root of 21531845 is about 4640.2419117973. The cubic root of 21531845 is about 278.2021070559.

The spelling of 21531845 in words is "twenty-one million, five hundred thirty-one thousand, eight hundred forty-five".