21510742 has 8 divisors (see below), whose sum is σ = 35199432. Its totient is φ = 9777600.

The previous prime is 21510733. The next prime is 21510743. The reversal of 21510742 is 24701512.

It is a happy number.

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

It is a Harshad number since it is a multiple of its sum of digits (22), and also a Moran number because the ratio is a prime number: 977761 = 21510742 / (2 + 1 + 5 + 1 + 0 + 7 + 4 + 2).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21510743) 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 3 ways as a sum of consecutive naturals, for example, 488859 + ... + 488902.

It is an arithmetic number, because the mean of its divisors is an integer number (4399929).

Almost surely, 2^21510742 is an apocalyptic number.

21510742 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21510742 is a deficient number, since it is larger than the sum of its proper divisors (13688690).

21510742 is a wasteful number, since it uses less digits than its factorization.

21510742 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 977774.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 21510742 is about 4637.9674427490. The cubic root of 21510742 is about 278.1111902751. Note that the first 4 decimals are identical.

The spelling of 21510742 in words is "twenty-one million, five hundred ten thousand, seven hundred forty-two".