20421999 has 24 divisors (see below), whose sum is σ = 33153120. Its totient is φ = 12019392.

The previous prime is 20421997. The next prime is 20422001. The reversal of 20421999 is 99912402.

It is an interprime number because it is at equal distance from previous prime (20421997) and next prime (20422001).

It is not a de Polignac number, because 20421999 - 2¹ = 20421997 is a prime.

It is a super-4 number, since 4×20421999⁴ (a number of 30 digits) contains 4444 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20421997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1104 + ... + 6485.

It is an arithmetic number, because the mean of its divisors is an integer number (1381380).

Almost surely, 2^20421999 is an apocalyptic number.

20421999 is a deficient number, since it is larger than the sum of its proper divisors (12731121).

20421999 is a wasteful number, since it uses less digits than its factorization.

20421999 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7631 (or 7628 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 20421999 is about 4519.0705902873. The cubic root of 20421999 is about 273.3376251887.

The spelling of 20421999 in words is "twenty million, four hundred twenty-one thousand, nine hundred ninety-nine".