21979129 has 8 divisors (see below), whose sum is σ = 22797000. Its totient is φ = 21165312.

The previous prime is 21979121. The next prime is 21979151. The reversal of 21979129 is 92197912.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3686400 + 18292729 = 1920^2 + 4277^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 21979129 - 2³ = 21979121 is a prime.

It is a super-2 number, since 2×21979129² = 966164223197282, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21979091 and 21979100.

It is not an unprimeable number, because it can be changed into a prime (21979121) 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, 14017 + ... + 15505.

It is an arithmetic number, because the mean of its divisors is an integer number (2849625).

Almost surely, 2^21979129 is an apocalyptic number.

21979129 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21979129 is a deficient number, since it is larger than the sum of its proper divisors (817871).

21979129 is a wasteful number, since it uses less digits than its factorization.

21979129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2027.

The product of its digits is 20412, while the sum is 40.

The square root of 21979129 is about 4688.1903758273. The cubic root of 21979129 is about 280.1152969049.

The spelling of 21979129 in words is "twenty-one million, nine hundred seventy-nine thousand, one hundred twenty-nine".