21669021 has 24 divisors (see below), whose sum is σ = 34879104. Its totient is φ = 12850560.

The previous prime is 21669019. The next prime is 21669029. The reversal of 21669021 is 12096612.

It is not a de Polignac number, because 21669021 - 2¹ = 21669019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21669029) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2325 + ... + 6981.

It is an arithmetic number, because the mean of its divisors is an integer number (1453296).

Almost surely, 2^21669021 is an apocalyptic number.

It is an amenable number.

21669021 is a deficient number, since it is larger than the sum of its proper divisors (13210083).

21669021 is a wasteful number, since it uses less digits than its factorization.

21669021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4721 (or 4718 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 27.

The square root of 21669021 is about 4654.9995703544. Note that the first 3 decimals coincide. The cubic root of 21669021 is about 278.7916508241.

The spelling of 21669021 in words is "twenty-one million, six hundred sixty-nine thousand, twenty-one".