21492739 has 4 divisors (see below), whose sum is σ = 21572320. Its totient is φ = 21413160.

The previous prime is 21492727. The next prime is 21492749. The reversal of 21492739 is 93729412.

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

It is a cyclic number.

It is not a de Polignac number, because 21492739 - 2²¹ = 19395587 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21492698 and 21492707.

It is not an unprimeable number, because it can be changed into a prime (21492749) 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, 39384 + ... + 39925.

It is an arithmetic number, because the mean of its divisors is an integer number (5393080).

Almost surely, 2^21492739 is an apocalyptic number.

21492739 is a deficient number, since it is larger than the sum of its proper divisors (79581).

21492739 is an equidigital number, since it uses as much as digits as its factorization.

21492739 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79580.

The product of its digits is 27216, while the sum is 37.

The square root of 21492739 is about 4636.0262078638. The cubic root of 21492739 is about 278.0335820239.

The spelling of 21492739 in words is "twenty-one million, four hundred ninety-two thousand, seven hundred thirty-nine".