21531994 has 8 divisors (see below), whose sum is σ = 35234208. Its totient is φ = 9787260.

The previous prime is 21531989. The next prime is 21532019. The reversal of 21531994 is 49913512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 489342 + ... + 489385.

It is an arithmetic number, because the mean of its divisors is an integer number (4404276).

Almost surely, 2^21531994 is an apocalyptic number.

21531994 is a deficient number, since it is larger than the sum of its proper divisors (13702214).

21531994 is a wasteful number, since it uses less digits than its factorization.

21531994 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 978740.

The product of its digits is 9720, while the sum is 34.

The square root of 21531994 is about 4640.2579669669. The cubic root of 21531994 is about 278.2027487724.

The spelling of 21531994 in words is "twenty-one million, five hundred thirty-one thousand, nine hundred ninety-four".