21506429 has 8 divisors (see below), whose sum is σ = 25426560. Its totient is φ = 17798256.

The previous prime is 21506417. The next prime is 21506431. The reversal of 21506429 is 92460512.

It is a happy number.

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

It is a de Polignac number, because none of the positive numbers 2^k-21506429 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21506489) 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, 52769 + ... + 53174.

It is an arithmetic number, because the mean of its divisors is an integer number (3178320).

Almost surely, 2^21506429 is an apocalyptic number.

21506429 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21506429 is a deficient number, since it is larger than the sum of its proper divisors (3920131).

21506429 is a wasteful number, since it uses less digits than its factorization.

21506429 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105979.

The product of its (nonzero) digits is 4320, while the sum is 29.

The square root of 21506429 is about 4637.5024528295. The cubic root of 21506429 is about 278.0926015200.

The spelling of 21506429 in words is "twenty-one million, five hundred six thousand, four hundred twenty-nine".