21351790 has 16 divisors (see below), whose sum is σ = 38712240. Its totient is φ = 8478720.

The previous prime is 21351787. The next prime is 21351791. The reversal of 21351790 is 9715312.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351791) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6291 + ... + 9070.

It is an arithmetic number, because the mean of its divisors is an integer number (2419515).

Almost surely, 2^21351790 is an apocalyptic number.

21351790 is a deficient number, since it is larger than the sum of its proper divisors (17360450).

21351790 is a wasteful number, since it uses less digits than its factorization.

21351790 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15507.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21351790 is about 4620.7997143352. The cubic root of 21351790 is about 277.4244687977.

It can be divided in two parts, 213 and 51790, that added together give a triangular number (52003 = T₃₂₂).

The spelling of 21351790 in words is "twenty-one million, three hundred fifty-one thousand, seven hundred ninety".