21021929 has 4 divisors (see below), whose sum is σ = 21187584. Its totient is φ = 20856276.

The previous prime is 21021899. The next prime is 21021953. The reversal of 21021929 is 92912012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021929 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021898 and 21021907.

It is not an unprimeable number, because it can be changed into a prime (21021989) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82637 + ... + 82890.

It is an arithmetic number, because the mean of its divisors is an integer number (5296896).

Almost surely, 2^21021929 is an apocalyptic number.

It is an amenable number.

21021929 is a deficient number, since it is larger than the sum of its proper divisors (165655).

21021929 is a wasteful number, since it uses less digits than its factorization.

21021929 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165654.

The product of its (nonzero) digits is 648, while the sum is 26.

The square root of 21021929 is about 4584.9677207152. The cubic root of 21021929 is about 275.9884166881.

The spelling of 21021929 in words is "twenty-one million, twenty-one thousand, nine hundred twenty-nine".