21390492 has 24 divisors (see below), whose sum is σ = 50003856. Its totient is φ = 7116928.

The previous prime is 21390491. The next prime is 21390493. The reversal of 21390492 is 29409312.

It is an interprime number because it is at equal distance from previous prime (21390491) and next prime (21390493).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21390491) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6808 + ... + 9440.

It is an arithmetic number, because the mean of its divisors is an integer number (2083494).

Almost surely, 2^21390492 is an apocalyptic number.

It is an amenable number.

21390492 is an abundant number, since it is smaller than the sum of its proper divisors (28613364).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21390492 is a wasteful number, since it uses less digits than its factorization.

21390492 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3317 (or 3315 counting only the distinct ones).

The product of its (nonzero) digits is 3888, while the sum is 30.

The square root of 21390492 is about 4624.9856215993. The cubic root of 21390492 is about 277.5919863865.

The spelling of 21390492 in words is "twenty-one million, three hundred ninety thousand, four hundred ninety-two".