21692021 has 4 divisors (see below), whose sum is σ = 23360652. Its totient is φ = 20023392.

The previous prime is 21691979. The next prime is 21692063. The reversal of 21692021 is 12029612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21691979) and next prime (21692063).

It can be written as a sum of positive squares in 2 ways, for example, as 14326225 + 7365796 = 3785^2 + 2714^2 .

It is a cyclic number.

It is not a de Polignac number, because 21692021 - 2²² = 17497717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21692071) 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, 834296 + ... + 834321.

It is an arithmetic number, because the mean of its divisors is an integer number (5840163).

Almost surely, 2^21692021 is an apocalyptic number.

It is an amenable number.

21692021 is a deficient number, since it is larger than the sum of its proper divisors (1668631).

21692021 is a wasteful number, since it uses less digits than its factorization.

21692021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1668630.

The product of its (nonzero) digits is 432, while the sum is 23.

The square root of 21692021 is about 4657.4693772477. The cubic root of 21692021 is about 278.8902545807.

The spelling of 21692021 in words is "twenty-one million, six hundred ninety-two thousand, twenty-one".