21407751 has 12 divisors (see below), whose sum is σ = 30964128. Its totient is φ = 14252544.

The previous prime is 21407717. The next prime is 21407783. The reversal of 21407751 is 15770412.

It is not a de Polignac number, because 21407751 - 2¹³ = 21399559 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407791) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9346 + ... + 11408.

It is an arithmetic number, because the mean of its divisors is an integer number (2580344).

Almost surely, 2^21407751 is an apocalyptic number.

21407751 is a deficient number, since it is larger than the sum of its proper divisors (9556377).

21407751 is a wasteful number, since it uses less digits than its factorization.

21407751 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3222 (or 3219 counting only the distinct ones).

The product of its (nonzero) digits is 1960, while the sum is 27.

The square root of 21407751 is about 4626.8510890237. The cubic root of 21407751 is about 277.6666250334. Note that the first 4 decimals are identical.

The spelling of 21407751 in words is "twenty-one million, four hundred seven thousand, seven hundred fifty-one".