21510745 has 16 divisors (see below), whose sum is σ = 26915328. Its totient is φ = 16485120.

The previous prime is 21510743. The next prime is 21510757. The reversal of 21510745 is 54701512.

It is not a de Polignac number, because 21510745 - 2¹ = 21510743 is a prime.

It is a Duffinian 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 15 ways as a sum of consecutive naturals, for example, 15937 + ... + 17233.

It is an arithmetic number, because the mean of its divisors is an integer number (1682208).

Almost surely, 2^21510745 is an apocalyptic number.

It is an amenable number.

21510745 is a deficient number, since it is larger than the sum of its proper divisors (5404583).

21510745 is a wasteful number, since it uses less digits than its factorization.

21510745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1440.

The product of its (nonzero) digits is 1400, while the sum is 25.

The square root of 21510745 is about 4637.9677661666. The cubic root of 21510745 is about 278.1112032040. Note that the first 3 decimals are identical.

It can be divided in two parts, 215 and 10745, that multiplied together give a triangular number (2310175 = T₂₁₄₉).

The spelling of 21510745 in words is "twenty-one million, five hundred ten thousand, seven hundred forty-five".