21506129 has 8 divisors (see below), whose sum is σ = 21950400. Its totient is φ = 21065616.

The previous prime is 21506101. The next prime is 21506131. The reversal of 21506129 is 92160512.

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 21506129 - 2¹⁶ = 21440593 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21506098 and 21506107.

It is not an unprimeable number, because it can be changed into a prime (21506159) 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, 12527 + ... + 14139.

It is an arithmetic number, because the mean of its divisors is an integer number (2743800).

Almost surely, 2^21506129 is an apocalyptic number.

It is an amenable number.

21506129 is a deficient number, since it is larger than the sum of its proper divisors (444271).

21506129 is a wasteful number, since it uses less digits than its factorization.

21506129 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1879.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 21506129 is about 4637.4701077204. The cubic root of 21506129 is about 278.0913084467.

The spelling of 21506129 in words is "twenty-one million, five hundred six thousand, one hundred twenty-nine".