21991045 has 8 divisors (see below), whose sum is σ = 26537760. Its totient is φ = 17493840.

The previous prime is 21991027. The next prime is 21991069. The reversal of 21991045 is 54019912.

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

It is not a de Polignac number, because 21991045 - 2¹⁷ = 21859973 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21990998 and 21991016.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11391 + ... + 13180.

It is an arithmetic number, because the mean of its divisors is an integer number (3317220).

Almost surely, 2^21991045 is an apocalyptic number.

It is an amenable number.

21991045 is a deficient number, since it is larger than the sum of its proper divisors (4546715).

21991045 is a wasteful number, since it uses less digits than its factorization.

21991045 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24755.

The product of its (nonzero) digits is 3240, while the sum is 31.

The square root of 21991045 is about 4689.4610564541. The cubic root of 21991045 is about 280.1659093268.

The spelling of 21991045 in words is "twenty-one million, nine hundred ninety-one thousand, forty-five".