21991029 has 8 divisors (see below), whose sum is σ = 29359680. Its totient is φ = 14641536.

The previous prime is 21991027. The next prime is 21991069. The reversal of 21991029 is 92019912.

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

It is not a de Polignac number, because 21991029 - 2¹ = 21991027 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21991027) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1852 + ... + 6885.

It is an arithmetic number, because the mean of its divisors is an integer number (3669960).

Almost surely, 2^21991029 is an apocalyptic number.

It is an amenable number.

21991029 is a deficient number, since it is larger than the sum of its proper divisors (7368651).

21991029 is an equidigital number, since it uses as much as digits as its factorization.

21991029 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9579.

The product of its (nonzero) digits is 2916, while the sum is 33.

The square root of 21991029 is about 4689.4593505009. The cubic root of 21991029 is about 280.1658413802.

The spelling of 21991029 in words is "twenty-one million, nine hundred ninety-one thousand, twenty-nine".